Tenants are often lat and new owner tend to get very nervous.

The loan is with you, not with your tenant, so none of that means anything to them - in fact because you live in one unit and it's under 4, if you were self-managing you don't even have to abide by fair housing laws (at least on the federal level). 

From my experience working with over 400 investors, I’d recommend starting with house hacking—ideally a fourplex if you find a good deal, but a duplex works too.

I replaced my old water softener with an AQUASURE from Home Depot, and it works just as well as the one I had before (which came with the house).

Too tenant (yes tenant) friendly and I wouldn't want to lose my house.

I kept thinking it would get easier and less nervy as I bought more houses.

Or find a deal first then market it to buyers, then offer on the house and create an agreement with the seller & buyer?

(do not trust me to build the house, but I do know how to qualify you FOR the house.)

And on the houses I build I pay the lumber direclty myself I pay the roofer..

You've probably heard of big Landlords losing property, but only because they were flagrantly violating Fair Housing, running a slum, or otherwise egregiously violating the law.