I'll be doing the vast majority of the work (at a professional level) myself so I can afford to throw some more $$$ towards materials to really make the building stand out.

If you make sure to keep 6-12 months worth of expenses in cash reserves, you can continue to house-hack and expand your portfolio with a relatively low level of risk. 

But most importantly, lenders will demand a certain level of rent and net income, with a track record typically of three years at that amount.

Depends on your experience and comfort level.

For one, you must consider combined income as your level to qualify on income.I have it in my written criteria that if one applicant fails the screening, the whole group is rejected.Maybe you can reject because one has no landlord references.

Stocks are teetering at all time highs, interest rate rise is on the horizon, inflation is already here, state and federal taxes are absolutely going to rise at a level not seen before.

I have put them in but using not the cheapest, base level.

I never hear back from most but for those that do we go on to the next level of screening.Before posting an ad on FB Marketplace I'd suggest reviewing the current rents for your area and make sure yours is up there with these. 

I assume if you ask your lender for a no cost no fee refinance the rate will be 4.875 with APR 4.875  Ask for the APR which breaks down the cost of the rate averaged over first 12 months to get level numbers.

Be honest with yourself about your skill/expertise level...more people fail in this business than succeed.