I am still performing due diligence on the ARV but it looks to be in the 250-260K range after about 50K of rehab. 

I own a property that has an rent to own tenant upstairs who has no money and does not perform required maintenance, which has adversely affected my property.

I did however work out with the bank that after a year of performance, they will re-evaluate and potentially give me more cashout in the future.

Just co-mingle money 1 time, or self manage the properties or do any of the work on the properties yourself rather than hiring a property manager or contractors to perform the work and that can be used to pierce the veil. 

Other investors and lenders like to see overall performance first (overall gross and net profit, operating expense, annual return in percentage etc).

if you sold now you would break even at best.. but this is pretty much how rentals go.. your numbers are not out of the ordinary.. unless you take on HIGH risk low income rentals.. were they look great on paper but rarely perform as the paper indicates..

Will you be performing equal duties?

A good company in a strong market should be able to offer inventory with safe and consistent returns.

He finds it keeps his income consistent.  

Please note that you are obligated to pay back their 401k (regardless of the performance of your real estate investment).As an alternative to taking the loan, you could even purchase the investment property directly using funds in your Solo 401k (assuming you select a Solo 401k plan provider which allows you to invest in real estate).