One thing you might want to consider is how you might have become such an amazing builder in the first place.

An amazing builder, one that can plan and direct the construction of elaborate structures, needs to understand a fair bit of physics and engineering. Drafting, mathematics, and a host of other complex skills are also vital to be able to plan a construction that will not only stand up, but is also aesthetically pleasing. While a good architect in any era will be able to bring his own original ideas to the construction of buildings, an architect still needs a baseline of skills on top of which to build (get the pun?). And in the 14th century, in order to acquire these skills most builders needed to have been trained by an existing builder. This training, typically imparted over the course of several years of apprenticeship, would mean that a builder who set up his own studio would most probably be accepted as a guild member as a matter of course.

But “builder” wasn’t always a tightly regulated designation as others might be, and guilds worked in different ways in different communities (you tend to see lots of protectionism when you can take a fairly cheap raw material, like cloth, and turn it into something much more expensive, like clothes; but you also see guilds forming when there are large localized industries who want to protect themselves against external competition, like say fisherman in coastal communities; and commonly, the longest lasting guilds existed when there was a little bit of both). Because planning buildings could be a fairly unregulated industry, there are many cases of people from non-architectural backgrounds developing architectural careers. A common path was through sculpture: Michelozzo di Bartolomeo, for example, was trained as a sculptor but transitioned into architecture, taking over the more practical aspects of planning and drafting while his business partner, the more artistically skilled Donatello, oversaw the aesthetic side of things. Two centuries later Andrea Palladio, who would become the premier architect in Italy, followed a similar path: a master stonemason by training, Palladio got his big break as an architect when an aristocrat entrusted him with implementing architectural designs for his home. Painters and illustrators with a passion for architecture could also be expected to take up drafting and eventually oversee constructions (the painter Raffaello, known in English as Raphael, is an example of a painter who dabbled in architecture).

Construction could also be seen as a fairly practical and workmanlike profession, with elaborate designs often entrusted to individuals with the time to devise them and the money to construct them. A person with sufficient time and means could be expected to plan their own home, directing the work as they saw fit; and it would be up to the workmen to ensure the load born by the walls and beams wasn’t too much, while the sculptors and carvers were to ensure their decorations wouldn’t topple over. Master stonemasons certainly brought their own ideas to the table (in fact, skilled stonemasons were often in high demand, and could even be part of an aristocratic dowry) but people with more money than sense could also insist on taking things in the wrong direction; it’s not unheard of to hear of precarious add-ons like towers or turrets collapsing, and fire was a constant threat that often went unmitigated (not that people didn't know how to make fireplaces, but things weren't up to modern fire code standards either). In spite of this, there are many beautiful buildings from the 14th century still standing today, and skilled and experienced masons as well as self-trained architects were certainly numerous enough such that we can’t say people were totally winging it all the time. The planning of public buildings, like town halls or tribunals (some of which still stand today) could even be entrusted to important members of the community who might not have any architectural experience at all, but were the most trusted to oversee the work of stonemasons and sculptures, often ensuring that different guilds (whose taxes were often paying for the structure, and whose artisans were constructing it) were in agreement as to how the work was to go forward. Architectural competence could even be an outright expectation for some members of the community: in the 12th and 13th century Italian city of Milan, dynasties of the local aristocracy were expected to oversee the construction and maintenance public structures like gate houses and toll booths.

If by builder on the other hand you mean construction worker, it’s true that sometimes workers in cities could create strong guilds which rigidly policed who could perform certain work (thus allowing guild members to demand higher wages). The bastaixos of Barcelona are a fairly well-known example of workers doing precisely this. In these cases it could be very difficult indeed for an outsider to work alongside guild members regardless of skill, however fairly unskilled work like carrying bricks or stones could easily be substituted for other less regulated work like loading carts or barges. On the other hand, more skilled workers like stonemasons or carvers who for whatever reason were not members of the guild (as would be the case for displaced peoples coming to a community) might have no choice but to pack up and leave, moving to a different community without a strong guild keeping them from working (unless they were so numerous that the local guild couldn’t stop them from working at all, which did happen sometimes).

If you’d like to read more about the kind of career path that you could expect an architect to have during the Renaissance (which is a little bit after the time period that you’re interested in) I examined the life of the sculptor Raphael, which includes his relationship with the architect Michelozzo, in this overenthusiastic answer. And I wrote an even more overenthusiastic answer about the kind of work the architect Andrea Palladio was doing some 200 years later here, which you might also be interested in.