@Jeremiah Ellard IVThis appears to be a financial strategy question and not really related to the FHA 203k. 

I can't find where the Florida Supreme Court has answered the question, so it appears in Florida, it's an open question as to whether the OP's neighbor would lose a civil action.

One appears to come from the house, but the two others from elsewhere and they all stop in the middle of your yard.If the water is high enough in the window well, it will come in through the area around the window.

It doesn't detract from the function or appearance at all. 

Kevin  My initial reaction would be to recommend against this as it appears you are putting all your eggs in one basket, meaning real estate. 

I considered SFH where I'd rent out all the rooms and keep one to myself, but this seems risky since I'll realistically be away for months at a time and couldn't manage the unit/other tenants.Then I came across some listings that appear to be hotel rooms for sale, with basically the facilities I need (a bed, toilet, kitchen), a price point I can handle (270-500k$, I'd do 20% down), and fairly high HOAs (~1500$/m?).

It didn’t seem like a deal-breaker at the time, especially since the previous owners appeared eager to sell.

Virginia does not appear to be one of those states. 

From my investigation so far, it appears that they get wiped out when you Foreclose the Right of Redemption after a year and a day plus a month or two.

What happened with the last one that I analyzed was the primary was changed so significantly, by a flipper who appeared to have done great, that there was no way to determine value added by ADU.