@Brian Eastman I know solo 401k and employer 401k's are different, but that's about the extent of my knowledge.
Is it possible to take out a loan against a solo 401k the same as you would with an employer type 401k, and use that loan to do the OP's cabin idea? The profits could be used to pay back the loan at whatever the appropriate interest rate is and it would be something similar to dumping more money in to the 401k.
I'm not sure if the OP's goal was to use existing funds to develop land or to grow the solo 401k. Using the Solo 401k to develop the land might be a burden if he planned to DIY anything. If I understand correctly, if the property was owned by the 401k, the OP could't legally develop or manage the property personally. With the idea of simply borrowing money against the plan, the cabins would then be under the ownership of the OP so it wouldn't fall under the solo 401k rules of separation.
Just curious, thanks.