Solo 401(k) Deal Structure for Flipping

[Yinan Q.]

I am planning to open a solo 401(k) plan for myself and maybe my wife as well. Our goal for the solo 401(k) accounts is to 1) tax shelter tax for money we make from flipping houses; and 2) use the money to fund our future flipping deals. My question is how to structure my future flipping deals with the solo 401(k) accounts involved? Below are the scenarios I can think of:

1. Our Solo 401(k) will fund 100% of acquisition and rehab. In such case, all profit goes back to 401(k). The profit will also be subjected to UBIT tax. 

2. The solo 401(k) account will fund part of the deal, say 20%, we will personally fund the rest 80% with our own money. Profit will be split at 20:80 ratio. The 20% of profit that goes to the 401(k) will be subjected to UBIT tax.

3. The solo 401(k) account will fund part of the deal, say 20%. We will have a partner to fund the rest 80%. Profit will be split at 20:80 ratio. The 20% of profit that goes to the 401(k) will be subjected to UBIT tax.  

No. 1 is probably the simplest deal structure but is not going to happen anytime soon as it's going to take a well before there is enough funds in our solo 401(k) accounts. My question is that if No. 2 and No. 3 is possible?