When I house-hacked, way back in the day, I was happy to have supplemental rent from the other unit in my duplexes (I lived in two prior to moving to my now long-term home) that kept my net mortgage cost to something affordable.I worked on the properties while I lived there (a couple-three years in each) and then when I moved out, i was able to (just barely) cover the loan payment, taxes and insurance with the rent from both units.I was out of pocket when I needed to make a repair and paid the garbage and water bills myself for a while (until rents climbed a bit).

I'm seeing more investors take this on completely or as a supplement to their physical driving.

Remember that real estate is a marathon and to supplement your income with larger MF I would at least plan for 18 months of no income before commissions/fees/cashflow starts to kick in.

Often, the party pushing for this will need to get friendly by offering to foot the bill (or supplement) for common area upgrades. 

From what I read box 3 links to Schedule C (Business income) instead of Schedule F (Supplemental income), if I group them together is it going to throw up a red flag for the IRS?

With this in mind I feel that wholesaling would be a good starting point for me as I have little cash and would need to supplement my current income quickly.

The idea of being able to leverage my money >6.5 times using a 15% downpayment to buy single-family properties sounds like an appealing method to grow long-term wealth and supplement to my MFR portfolio.Finding a 1% property seems difficult in the several markets I have recently been analyzing. 

There is also a gas wall heater that provides 50,000 BTU, but I thought it would be nice to have a wall heater in each bedroom for supplemental heat. 

Either draw it down from 45-60 at the 4% rule to supplement me stepping back from the workforce or have the ability to sell off, pay the taxes, and chase opportunity

Second, since your outflows are the same, ask yourself how many months/years you could make supplemental payments if your were short on a mortgage with the tax you'll defer in the 1031 exchange?