You can get a US Trust for far less than $5000. I use
this firm.
However, all you really need is a US citizen who is willing to be the owner and who you can trust
The difference between this and using a more established outfit like the one above is that the latter will have a contract which protects both parties, and one of the things it does is it prevents the owner from simply running off with the plane. This is why you need to be a bit careful who you use if you do it informally - the owner does fully own the plane and could run off with it.