Legally speaking, if you have proof of transaction, than you own the right to use those builds in your game (assuming those were the direct terms of the transaction).
Intellectual Property is a tricky thing, however if you hire a builder to create something for you directly, or for your corporation, etc, you would own the rights to that IP.
While slightly different, it is essentially the same thing, however in this scenario you are purchasing rights to use that intellectual property.
For a concise answer, you wouldn’t even have to worry about it being taken to court as most judges would throw the case out due to the IP being properly purchased.