How can you structure a Solo 401K with Sub2

[Clay Smith]

I have found a duplex for $89k (asking price). Both 2 BR, 1 Bath units are currently rented for $550.00 per month. Owner pays water/sewer ($50 mo).

The owners are willing to entertain subject to (Sub2) financing. How can I structure a deal using my wifes old employer 401k to make this deal happen? I was unsure about the exit strategy. Most Sub2 are short term loans. She has $23k in the account. It is not a ROTH.