Rent by room is an option that many people do here but even then it's not easy, and several randoms living under the same roof calls for its own problems and likely a lot more turnovers, so I'll see.

On top of that you can find some great deals on TLC properties that need a little work but offer a strong ARV to expedite your initial cash back out with room for the next REI down payment.  

Your visits to the home seem to upset him, if you don't enter his room and your son is living there depending on the lease wording there probably isn't a violation.

Depending on the location and properties, consider having a game room.

Nice to have the breathing room, and I'll def keep tracking what happens to make sure to predict this and any possible future investments!

They have close family in the area they invest, perhaps even living in the investment property itself like their child who is a college student and rents other rooms in the house to friends, or their sibling or parent.

Quote from @Chris John: @Georgy Cherkassky"Not entirely, if your saving 1 grand a month for a downpayment on property; your first property will be in three years and then you will have to save for another 3 years to buy a second property, so on and so forth."

You should definitely buy a property and give/rent out rooms to the homeless and disadvantaged.

You may want to live in a world of Wild West, anything goes business (I won't mention the orange haired political elephant in the room) but I assure you, your ignorant, uninformed, and weak defense of this sort of activity is not common.

A bit pricey, but at land value there's definitely some room.