•Strong Financial Returns: With typical CAP rates around 9%, and an average cost of approximately $530,000 for a three-bedroom, two-bath fourplex, investors can expect an annual income of over $60,000.

I'm not bold enough to buy real estate at negative leverage - few deals in my area (and I presume, Manhattan), are trading at "Cap Rates" greater than 7%. 

Also, eventually, the renovations are out of date or worn and you need to do another cap ex spend. 

I actually did look into this but it wouldn't be ideal for me since cash advances are capped at a percentage of your overall credit card limit which is usually at 30% more or less.

I think most locals are aware of the history of STRs proposals/cases in Portsmouth, Laconia’s existing restrictions limiting non-owner occupied STRs to resort/shorefront only, VT's local option tax that allows a 1% tax above the state's existing 9% tax, Portland cap on STR permits and increases tied to inflation, and it's also probably a good idea for folks to understand NH's Senate Bill 249, which proposed a "ban of local bans" around STRs and basically died on the floor(?)

While this would improve the cashflow and cap rate for resale, I'm wondering if it would shrink my market of buyers, since they could no longer use conventional financing as it would no longer conform to a 2-4 unit building.

Will be running at a 20 cap if we get all 7 to $1100, which I think is possible. 

Based on a quick analysis, you're looking at a ~4.2% cap rate (Before Debt).

Less seasoning, no cap on how many mortgages you can hold at one time.

Bringing the gross rental income to $5,800 - $7,500 a month before expenses and cap x.