I typically am working with suppliers of red iron beams, but I would imagine suppliers would still have something.https://www.engineeringtoolbox... is a great free resource for information on different types of materials.Hope this helps at least some!

My heart skips a beat as I imagine the bills of digging a new gas supply line out to the street.

I would go with "3) get a structural engineer to "stamp" it and say that it's up to code" Can you imagine what you'd be in for if someone died in an un-permitted bedroom when you have knowledge and have been notified by the city?

One can imagine this makes it difficult (ie more costly) when adequate guidance is not given.

So imagine if property appreciates only 2% in a bad year but you have 20:1 leverage?

So if it is listed on both services, I can't imagine google/meta/tiktok ads will help.

I could imagine it getting very tricky with a 3rd party management company and have not heard of a company doing it.

I imagine you already did this - but if not - review your CC&Rs to confirm that MTR/STR is allowable in your neighborhood.

If you find a bank willing to play ball I would imagine a few people on here would like to know which one. 

I would imagine the $4000 to $5000/mo net income is on the high end.