It's the boring places that probably won't appreciate above the rate of inflation that will provide real month to month income. 

Westchester, although one of the hottest markets, has a ton of upside with opportunities for both cash-flow and equity. 2-4 family properties in Westchester are the 2nd most affordable in the NYC Metropolitan area (next to Suffolk County) making it easier to find cashflow opportunities when compared to the boroughs and other suburbs like Nassau.A client of ours in Westchester recently purchased a < $800K 2-family with a detached 3-car garage which brings in additional rental income - from a local business owner with commercial vehicles.

The income of a property manager is dependent on whether you property is filled with tenants as well. 

They choose to because we earned it.

To Sum it up, its a good idea if you can exceed the cost of capital (higher rate than your cost of debt) with what you earn on your heloc/debt you pull out and invest.The question is how much gains above is enough to substantiate the risk of your variable interest rate, well thats up to your personal investing criteria.

After five years, you'll have earned $90,000 in rent income and gained $34,000 in appreciation.Buy four houses with $50,000 down on each.

Given your experience with RV parks and MHPs, you already have a strong foundation for managing mixed-income streams, which will be valuable here. 

Question that the “believers” don’t ask is “how much could I earn on the extra money I’m spending to pay down the loan faster?  

As a US citizen I have an SSN, file taxes every year on my foreign employment income, hold US-domiciled assets (stocks, IRA, 401k), and I have a ~15 year credit history with a decently high score.

As in; they do ___, earn ___, and WANT ___ & ___ & ___ and thus, "the government should" make everything they want conform to there affordability.