Are you aware that a percentage of rent on additional units of MF can be used as income to qualify for the loan? 

In addition: I would withhold more money for completion.

Used a HELOC on a primary, and was sure that even with that additional debt-service, there was + cash flow.

Depending on the cash flow and your FICO, you should be looking at 75% or 80% (80% will have a significantly higher rate than the 75% but depending on your strategy could be worth looking at) of the new as-is value that you can get to pay off the rehab loan and get some cash back to go after your next property.I'd recommend looking at some of the BRRRR articles that have been written in the BP forums for some additional info on this process.

So, if you have a W2 or cash flow from properties to build some reserve funding over time, then I would likely say know to additional funding from the cash our refinance.

But we also know that the materials he employed on the Usonian houses are not exactly affordable by today's standards... 

This is still a good investment in my opinion.Feel free to reach out if you have any further questions or need additional clarification!

Because the original value of your closed loan was based on renovations being done, there is no additional value to use for the removal of the PMI.Maybe consider refi to another lender who will order another AVM or appraisal to get you a more desirable LTV. 

The minimum down payment for a property in this price range would be roughly $27K.That said, you also need to account for bank closing costs, inspection costs, appraisal, attorney fee, and title costs.Your scenario may require a seller's concession to account for these additional expenses.Investing with $50K is totally possible in this market but your journey may be met by challenges i.e.

Unfortunately, she frequently turns it off to save on electricity, which exacerbates the issue.i have also sent her extra radiator heat so can just plug in , but she refuse to use because she has to pay high electric bill.She complained about the unit's insulation and requested that we install an additional baseboard heater( whats the use if she doesn't turn on the heat) .