Early Withdrawal from Solo 401k my only option?

[Judd Campbell]

Looking at a Multi family project and the bank is willing to do 15% down however not with a Solo 401k due to the non-recourse loan requirement.  I don't have enough to put down 40 or 50% and I don't want to miss out on the deal.  

If I pull out for instance $100k, I get hit with a 10k (10%) penalty then taxes (assume 25% federal, 5% state) on the full 100k as well right?  so I would only net 60% of the balance after the dust settles.

I have enough to make up the other 40% in non retirement money so I can still close the deal.  I feel like it is worth it as I have been loaning that money out and getting a return of 12-15% but it has been just doing short term hard money loans.  I have purchased a few smaller multi-family places with the Solo 401k but use the cash distributions from those properties to go right back into the account. 

The loan approach is maxed out at $50k I understand.  that will not be enough.