It was mostly due to my day job income and low cost of living over a long period of time; however, real estate accounts for about 50% of our income through a small portfolio of short, mid, and long term rentals. 

I own several hundred rental units in other states, otherwise I'd join you in helping cover the costs.

The primary risks at this point would be       1) to your lender, the risk of a margin call.       2) To you; underestimating the true cost of a project and cost overruns      3) To you; legal risk of securities regulations if you partner looses money. 

If you are going to raise equity, you appear stronger if you can originate bank debt at a lower cost than alt. lenders.

You need to know what things cost.

@Martti Eckert in our opinion, you'll need to be really familiar with construction, including costs, or be able to find somoen on the ground you can REALLY trust (but still verify).

We got started, but they hired an appraiser and charged me $750, while typically appraisal costs around $500.

Vacancy hurts a bit more, but the biggest issue with renting out large homes is turnover cost.

Your estimate seems low, but even at that cost, it will not add that value.  

Then there is the time element with holding costs.