I've never heard of a one. The thing is that the writing was emphatically not on the wall. We think of it that way because we know how the war shook out, but they didn't.

Most white southerners believed that the war would be over fairly quickly or, even if it ground on, that the Confederacy would win in the end. They also had a decade of boom under their belts which encouraged them to double down and, from their POV, independence removed the chief threat to the security of slave property which might encourage cashing out. The future was full of profits with slavery as an ever-advancing, dynamic system of torture for profit and no end in sight. Their system was not ailing or necessarily backwards from their POV and they had the account books to make the point for them. The only place they'd seen serious and concerning reverses was in national politics, where the white South's nearly absolute control of the federal government and de facto veto over national policy was finally and just barely overcome in the election of 1860. What drove the white North to that was not Southern weakness in any absolute sense, but rather a string of remarkable advances for slavery which generated a backlash that the customary and constitutional framework purpose-built to preserve the institution could not fully contain. With that problem sorted by revolution, why would anyone cash out?

As far as I'm aware, no one in the Confederacy sold their slaves. The Confederate project was explicit to preserve slavery, and anyone invested in the project necessarily believed it would continue slavery. And no one sold their land. It was still productive farming land and the slave system was not necessary to produce plantation goods like cotton. It just made it more profitable. Many plantations continued to produce agricultural products after the Civil War.

It was different on the Union side. While the majority of slaveholders who were loyal to the Union were not abolitionists, they were more aware of the possibility of abolition. The Federal government was also less hostile to them, even as it pressed ahead with abolition. Even among some abolitionists, there was a sentiment that loyal slave owners were not to be treated as harshly as Confederate slaveholders. There were state and federal attempts at slave buyouts (as succeeded, for example, in DC in 1862). As the Union became increasingly anti-slavery, the Union slave owners increasingly sought to preserve their position through non-slave means.

This usually meant finding some way to get wealth or productive enterprises that were not slave based. (There was a great increase in slave owners putting their money in non-slave ventures during the Civil War.) But it also included getting what value they could get for their slaves. However, most were not compensated. This does not mean they were as impoverished as their Southern counterparts. Crucially, their plantations were also not damaged by the war. Where they were, they could count on aid that was not attached to a military occupation like in the South.

This made the transition much smoother. The average Northern slave owner lost their slaves but kept all of their land, belongings, ownership of farm implements, etc. And they did it without the disruption of an army moving through. Many did things like start other businesses. Some impressed on slaves how good it was to have a master that wasn't as bad as those evil Confederates to convince them to stay on afterward. (To, it must be said, varying degrees of success.) Perhaps the cleverest one was a Maryland slave owner who took out a large loan collateralized by his slaves. When Maryland freed their slaves in 1864, he defaulted on the debt and kept the money. The creditor could not repossess what was no longer property.

All that said, even if a slave owner had wished to 'cash out', it would have been increasingly difficult. As the war went on, slavery became increasingly non-viable in the North. For example, once slaves were allowed to sign up for the Union army, slave markets largely disappeared. Any slave brought to one was liable to run away and join the Union army. In addition, the general pattern was that slaves were sold into the Deep South. That was Confederate land and so closed to trade.