Still, I think one of the biggest problems a lot of elderly people face is feeling isolated and lonely and the best business opportunities are offering solutions to other people's problems.

I've worked in network for decades and there's lots of issues here.For the owner, you could provide a subscription service for each tenant & deny all other access, BUTif all tenants connect to your modem or router, you create a security risk for everyone.Pre-wiring would require a setup like:ISP==modem--router--- to units and this generates access from one unit to the other.for a more secure layout you need an extra router for each unit and someone to set a unique address for each router - - and this isolates each unit from the others.In either case, notice there's only one ISP so everyone has the same level of service and you'll need a big bandwidth to support multiple units. 

This will isolate assets from each other (you couldn't lose more than the actual property).

Either way isolate the problem then proceed to do it yourself fix, rent a power auger from a rental shop and start snaking.. if you fix it you've gained knowledge and experience that you can use from now on.

The damage seems to be isolated to a specific corner the basement.

Plus, you'll be able to tell if it was an isolated incident.

Isolate and test until you find out where the smell is coming from.

The wifi is set up to isolate the three clients (Teinentes 1 and 2 and my surveillance equipment) with their own SSID (wifi name) and passwords (set by me) they will not have access to each other’s network (isolated clients).

If you are going to analyze the profitability of a deal you would want to isolate all of those items to obtaining that deal and not comingle with other operational costs.  

I’d rather be a little north on there or if price is a dealbreaker maybe consider Baltimore or it’s surrounding counties it’s a little isolated down there which caps both appreciation and rent growth.