It's a forced equity and appreciation play with the benefit of personal use and the hope that 100% bonus depreciation comes back.

I would like to have lower monthly payments should I make a big lump sum payment towards my principals and ask my mortgage company to adjust it or refinance it or which one is the best ? 

They will mostly just split their occupancy rates on multiple platforms without getting too much benefits out of it. 

Don’t forgot to look at all the ways properties make money: Appreciation (#1 way), equity gain through principle pay down, tax benefits, positive cash flow (never as much of a wealth-builder as appreciation is in good markets).

Side benefits or PM besides free time.

Using a heloc as 1st mortgage really only has a major benefit if you have idol cash sitting around from your paychecks. 

If before getting a permit you have to dance around for Code Dept officials/ city gov and crime is thru the roof, investments will definitely be low whether real estate or other, but it should be benefiting the city officials to keep things that way.

It will familiarize you with the basic terminology and benefits.

As I wrote in another reply too - one more benefit for me is that in a way it's "forced savings" - I have to find a way to pay the bill...

Possible add insurance on your appliances with them paying by adjusting the rent or if they are OK with it so if something else breaks,your covered.