You don't look for distressed, or blue doors or any other BS indicator you just get interacting. 

Quartz countertops, fully tiled bathrooms, higher ceilings and doors, LVP flooring throughout. for us its upgraded appliance packages NO micro above the drop in stove.

It will still cash flow at about $200/door/month if anywhere near full occupancy.  

Say there’s a way to sidestep the door-opener issue.

$500,000 after taxes is likely close to $325,000(maybe more or maybe less).Assuming cash-flow from rentals is offset by depreciation, you would need $325,000 of annual cash-flow from the rentals.If you can get $200 / door / monthYou would need 135 doorsYou can work on this type of math to figure out how much rentals you need.Be mindful that rentals require some type of work.

I have contractors and home warranty for each of the 8 doors.  

Best way is door knock, cold call and do the dirty work to find those sellers needing to sell.

It's a great way to get your foot in the door in your local market and offset your mortgage while building equity. 

Did you check a next door comp that just went into contract?

.- Most cities do NOT care if an owner lives in basement, but will not allow a tenant to unless baement has legal egress window.3) Check local statutes if any limitations on how many unrelated roommates are allowed.4) Check with local building dept to see if rental inspections and corresponding requirements.5) Local statutes allow locks on bedroom doors?