We are doing this with a portfolio lender and paying a bit of an interest rate premium as we are over the limit for Conventional financing. 

I've tried perusing the California tax laws and it taxed my limited brain capacity, so I had to give up.

Only limiting it to 3 things is tough but I’d say the 3 most important things I’d recommend to newbies are:1.

Along these same lines, an app like Venmo may work with a prepaid card (registered to a network brand like American Express, Discover, etc), but the issue with the daily/monthly send limit would be an issue I think. 

James Kleimann of HouseWire reports that starting April 1st, a number of new restrictions will take place including a 7% limit on Fannie Mae’s acquisition of single-family mortgage loans secured by a second home and investment properties.

However you may have limited time to make a claim.

So far I've checked with one and they don't offer an FHA Loan and for conventional you need 25% down for a triplex whether it is primary residence or not (unless you go Home Possible but I don't qualify because they have income limits).

Also, I have my own capital that I could use in a conventional mortgage that would secure long-term financing, but doing that would probably limit the number of loans I can take out.If they’re giving me this real estate loan in part because of the I have as collateral, does that mean that I can’t use that capital for other things?

You are bumping into the standard conforming residential loan lower limit. 

Since we live in Texas and due to the moratorium in place and no evictions I was limited about options and I sense he took advantage of that .