It's Mid-May 1945, I am a 35yr old Jewish Doctor. I’m in Southern Germany and am just now coming out of hiding. I miraculously was hidden in my hometown, in Southern Germany. My town was largely unscathed by the war and Americans are roving our town. I've been told by my hosts that my former house is still standing, though a German couple moved into it during the war.
What an incredible story, Dr! It is not terribly unbelievable either, but highly unlikely; or, as you said, simply miraculous. I would venture to say you have probably been in various stages of hiding since 1933. Beginning in April 1933, you would no longer have been able to practice medicine due to the anti-Jewish business boycott, though you may have been able to continue practice informally in peoples homes, etc; Dachau, the first camp, is also built this year. By October 1938, your passport is invalid; only a month later Kristallnacht occurs and by this point you have probably realized the severity of your situation. You are probably in Württemberg or Bayern or Baden; Baden is a good choice for your scenario since real support for the NSDAP was not as strong there as it was elsewhere in Germany, its entirely possible that you've been hidden by a friendly family. But since you are in the American Zone, it is more likely you are in Bayern or Hessen.
But your question concerns your property, now that your person is safe. Your personal property is almost certainly gone. If you were smart enough to bury valuables or entrust them to your friendly host family, then it is possible you are not completely broke. Not being allowed to practice medicine for years has deeply affected your savings. If you were rather well off, perhaps you had a foreign bank account in Switzerland or Britain; that should still be accessible and will help to establish your identity.
The very first thing for you to do is establish your identity. This will be crucial for moving about your city during the Allied occupation as a relatively free person; though your passport is invalid, you might still have your ID papers -- branding you as a Jew, of course, but having your real name. Right now, the Allied priority is assessing the immediate post-war situation, enforcing law an order among the population, and demilitarizing what remained of the German war machine. So, I am sorry to tell you Doctor, but you probably have no hope of reclaiming your property for many years. You are also of course not alone in your claim; a great volume of claims will be coming in the next decade and beyond.
In fact, no legal provision existed for property restitution until 1953. Several rounds of laws were passed and subsequently amended throughout the 1950s and can be understood in two broad categories: one set of laws to deal with financial payments as restitution for damage to your person and the other set of laws to deal directly with expropriated property. This is quite a mouthful, but the first of these laws were called Bundesergänzungsgesetz zur Entschädigung für Opfer der nationalsozialistischen Verfolgung (BErG) or the Federal Supplementary Act on Compensation for Victims of National Socialist Persecution. It only existed in the Federal Republic of West Germany; had you been liberated by the Soviets, its likely you would never be able to make this kind of claim.
From 1945 to 1953, without a legal framework in place, you would have tried to return to as normal a life as possible while you gaze through the open windows of your former home watching this German family wipe their feet on the same rug that belonged to your great-yenta great-bubbe. Though you haven't practiced medicine in over a decade, during the immediate aftermath the Allies would probably make use of you and you could later reopen your practice to service both occupying soldiers and civilians. You are most likely living at one of the many Allied-run displaced persons camps; these were initially built to house liberated prisoners from concentration and death camps. Life is very difficult at these DP camps; there are shortages of everything, but because you are a hardworking Jewish doctor, your dedication to treating concentration camp survivors earns you a few extra rations and a privileged place in this society. You have a decent chance of at least finding out what had happened to your relatives; at least several of them are dead, and if you had wife and children, their best chance would have been to flee the Reich prior to Jewish passports being invalidated.
Some pretty specific criteria had to be met to apply for financial restitution under these laws. You would need to be able to prove 'damage to life, health, freedom, property, property or professional advancement through a National Socialist measure of violence'. As long as you are honest, this should not be difficult; the host family that saved your life would be able to corroborate your story if necessary, and since your town is relatively untouched by the war, it is likely still possible to examine public records and see your medical practice on the books prior to the passage of anti-Semitic business legislation. You also had to prove that you were German or otherwise immigrated to Germany prior to 1937. I would think that proving your business losses would naturally prove this condition as well. You would be able to claim all the real property of your former business, though the property itself is long since gone, likely seized by the NSDAP for the war effort during your period of hiding. You would also be able to claim personal effects you had to surrender, such as clothing, luggage, etc. If you owned any fine art or jewelry, these are claimable as well. You are also able to claim loss of life; if you found out that your immediate family had perished, you would be able to apply for compensation for this as well.
After submitting these claims, its much the same as dealing with any government institution: just wait. As previously stated, the volume of claims and competing immediate priorities in restructuring Germany will all affect the speed at which you receive your compensation.
By this point, the German family has been living in your former home for probably over a decade and have a more legal claim than you do to it at this point. They have a legal deed, whereas you cannot prove you ever owned this home; the NSDAP would have invalidated and/or destroyed records of you owning real property. It is likely you'll never set foot in this home again. It maybe, maybe possible through circumstantial evidence to prove that it was once yours and you were deprived of its full value, and thereby achieve some financial restitution you could use to buy another home, but that is probably your best bet.
Finally, a last bit of trivia about these restitution laws: applying under these laws expired on December 31, 1969, though the laws still exist mainly as the legal basis for continuing to pay out pensions.
/u/gingeryid gave an excellent expansion of the answer concerning reuniting with lost loved ones. I think that question alone merits several long answers; this user with Jewish Studies flair does it concisely and well. If you enjoyed my answer, please read their addition as well.
Edit: Wow, thanks for the awards! First gold for me. I had a lot of fun writing this and reading about this topic, as morbid as it is.
Jewish Virtual Library, Holocaust Compensation and Restitution by Country
Transcript of a newspaper article from 1957 concerning the German restitution laws
Arnold Lehmann-Richter, The judicial assessment of retroactive changes in law in the law of reparation (December 11, 2002), in forum historiae iuris, https://forhistiur.net/2002-12-lehmann-richter/
Problems of Compensation and Restitution in Germany and Austria
For further reading, here is a bibliography on the topic of property restitution during the Second World War from the US National Archives
There is also this exhaustive source. Immoveable Property Restitution Study, European Shoah Legacy Institute.
/u/Cyberpunkapostle gave an excellent answer on recovering property. I'd like to fill in a specific component of this--finding out what happened to your relatives.
This was, as you can probably imagine, a massive effort. Survivors of the Holocaust had been displaced in huge numbers, and since they were generally separated at some point from family members (for if they hadn't, they would've died too), they had to re-link-up with family. Because the Jewish populations of whole towns had been killed or nearly the entire Jewish population had been killed, people might've had to do a lot of searching to find anyone they knew before the war. To compound things, surviving family may've survived because they were overseas, in which case they weren't around to ask people if they knew what happened.
If you lived in Germany in hiding, you would have an incredible advantage in this regard, since you were still in an identifiable place. If your family had, say, been caught and deported, they could come back and look for you--and if you were out of hiding and acquaintances knew it, your relatives could come to your hypothetical German town and ask about you. If you hid and/or were living somewhere else after the war, you could even visit or write to prewar non-Jewish acquaintances, so if a relative came around asking about you, they'd find someone who knew.
For other survivors, you could try the old fashioned rumor network. You could ask around the DP camp if there's anyone from such-and-such town, and if you found them, ask them if they know what happened to so-and-so, and if they didn't, maybe they'd be able to know who would--either at that DP camp, or someone else you could write to. One structure that might be helpful in doing these were "Landsmanshaften" in America. These were organizations formed by immigrants to America from specific towns--which shows the size of the Jewish immigration to America in the early 20th century, you could have a whole organization of people from a specific town in one Jewish neighborhood! Sometimes they had a joint-aid scheme to support each other financially, often they had burial organizations, often they started synagogues (which generally are the only Landsmanshaft-founded organizations that still exist). This meant that if you, in America, wanted to know the fate of your siblings or cousins or parents still in Europe, you might know people who also had family in the same town, who could provide information. Sometimes groups of survivors from specific towns centralized their efforts at cataloging who survived and who died. And if you lived somewhere without a local presence from your hometown, maybe you would know someone who could get in touch with such a group in another city.
But obviously that takes a long time, and breaks down quickly for bigger extended families or cases where "going back" wasn't safe or desirable (which was true of most of Eastern Europe), or cases where people didn't really have non-Jewish prewar friends of acquaintances, or none who'd survived, or for children.
Several organizations filled in the gap. The biggest, and most famous, was the Red Cross, which set up the "International Tracing Service". This was an archive, effectively, that got the Nazi-era documentation available, and combined it with postwar documentation (e.g. paperwork filled out at DP camps). Now the archive is public, but previously you would request information on someone. Nowadays it's searchable, though now it's mostly useful for descendants seeing records from their ancestors or other family, rather than finding who survived.
Many other organizations worked to produce lists of survivors. These lists would include people known to have survived. Someone searching for their family could consult this list (or more likely, find an organization that had the list), and if a family member appeared, try to find them. Some libraries still have such lists. That list is by the Jewish Agency, which worked with survivors who moved to Israel after Israeli independence (and with Israeli families looking for their relatives in Europe). They also compiled lists of people being looked for, and recorded information from people if they knew someone's whereabouts (i.e. lists of people known to have died). They also had lists of people being searched for that were broadcast via radio. Smaller such lists were broadcast in some European cities. Other organizations, like the American Jewish Joint Distribution Committee ("the joint") or the World Jewish Congress did similar things.
Ultimately, though, it sometimes just didn't work out. There many people whose relatives probably died, but never could confirm what exactly happened. Sometimes they might've had some information--a name that appeared on a transport list to a death camp, for instance, or an account that "all the Jews of such-and-such town were killed". But sometimes not that either. There are people who were known to be alive through much of the war and just never reappeared. Presumably they were murdered, but there's just no way to know--or provide their families with closure. The most pressing cases were for people whose spouses were unaccounted for, who under Jewish law could not remarry (unless, if they were men, they received permission from 100 Rabbis from 3 countries and wrote a divorce for their presumed-dead spouse). Considerable effort by Rabbis after the war was spent in establishing how people could be proven dead, which generally resulted in people being able to presume their spouses were dead.
This process took years, though. Occasionally you do read about families reuniting after many years. Such a case could happen if someone really was sure their relative died, and didn't want to spend time searching in vain, or if they just got very unlucky and weren't looking in the same places. Generally, though, people found what information there was available, with the help of these many organizations.
Thank you for great questions and answers. I have enjoyed learning so much this morning. Thank you.