Yes you can use commission as sourced funds for down payment on a conventional loan.However some lenders have internal overlays that don't allow it.

If the answer is yes, then it's a no brainer to make minimum payments on your 2.8% interest rate mortgage, and use the funds that you would have paid extra to pay it down faster, to either invest in more real estate, the market, or anywhere else where you can get a ROI > 2.8%.If the answer is no, then feel free to aggressively pay it down as fast as possible, to become debt-free faster, and just have a large amount of money in savings or to splurge with.The bottom line is that your 2.8% mortgage is GOOD debt.

Lender wanted homeowner to sign something to recieve the funds.

You just need the right funding to make it happen.

I can buy a 2-4 unit with 20% down vs conventional can only buy a 2-4 INVESTMENT property with 25% down 4. there are options where DSCR loans dont repot to personal credit, helps in not having to show a bunch of paperwork or not one person in a partnership has to carry the debt5. way less paperwork to close on this loan type vs a conventional loan. we care about the income of the property you're buying and it's ability to service the debt of the property whether we use long term rents income, lease income, or air dna/bnb income.6. easily buy in partnerships, add people to your operating agreement, its as easy as that so bring partners into a deal. helps with scaling and raising capital or getting partners involved7. gift funds allowed to close on these as well, and like I said earlier, there's only a 10day seasoning period of funds with some lenders so that means you can literally have a private money lender deposit money into your account 11 days before closing, and you can use those funds to close!

I have been on New Western's deal list as well as another bigger local company and everytime I underwrite these deals there is very very minimal left on the bone let alone contingency funds for going over budget on the flip...

While they mostly aren't lying, they leave out a lot of reality.Why would a government funded program like S8 pay MORE than market rents?

You could use the sale of your primary and the sale of your investment property to fund the purchase of the land and the beginning of construction. 

You have to have confidence and the Sponsor needs to build a relationship with you if he wants to be sure you have some insights into the risks of the types of deals you would be funding. 

If you're considering hard money loans, they can provide fast funding, but with higher interest rates and shorter terms.