Rented the two spare rooms in my own house and it covered more than I expected

The one page agreement is the part I'd copy. I'm planning my first purchase and I keep hearing that shared living blows up over dishes and parking rather than rent. Did you put anything in there about what happens when one of them wants out early, or is that in the lease itself?

Did you run credit and income on both of them, or did living there yourself change how you screened? I ask because I'm about to screen for a whole-unit rental and everything I read assumes I'll never meet the person.

Secondhand furniture at $840 for two rooms is good. Just know the desk chair and the mattress are the two things you'll replace first, and mattresses get expensive fast when you own five of them.

You found the occupancy limit after the fact and it worked out, which is the version of that story people don't usually get. I look at zoning for a living on the land side and the thing that catches people isn't the headline number of unrelated adults, it's how the code defines a family or a household in that specific jurisdiction, and whether separate written leases per room push the use into a different category entirely. Those definitions differ by state and by city. Pull the ordinance text yourself and if it reads ambiguous, email the planning department and keep the reply. Rigging, since you live there, you're likely in a much safer posture than someone renting all three rooms out, but confirm that rather than assume it.

One thing here still isn't clear to me. If utilities are included, what stops someone from running the AC at 65 all summer? Is that in your house agreement too, or is it just that you're standing right there?

Living in the house is doing a lot of work in this story and I don't think you're charging yourself for it. You're the manager, the cleaner, and the referee, and none of that shows up in your $1,290. Which is fine while you're there. It just means the number doesn't travel to a house you don't live in.

Coming from the build side, check that both rooms have a window that actually opens wide enough to get out of and that you've got interconnected smoke alarms. Egress and alarm requirements vary by state and by when the house was built, so ask your local building department what applies to yours. Cheap to fix now, ugly to discover after something happens. The rest of what you did reads sensible to me for a first go.