In addition to the constant tenant turnover, there are the various correspondence/questions and the need to immediately address various issues (the number of less than stellar reviews we have for downed WI-FI is not insignificant). 

I just don't know if it is worth it.Is it likely I will recoup any investment to address some of the fundamental issues (raise sagging floors in the lower unit plus addressing issues that will cause in the upper unit when the walls raise 1-2", replace galvanized piping, re-do the poorly done roof) when we look to sell in 10-15 years?

Then use whatever tools you have at your disposal (Skip trace, looking for numbers on LLC docs, looking for their number on MLS if it's an owner/agent, send post cards to their tax mailing address, etc) to get numbers for the managing membersHave a script you can use to call them and ask them if they are buying, what they're buying, price points, rehab level, neighborhoods, etc.The good thing about this strategy, although it's a lot of work, is that you are connecting with actual buyers who have actually recently closed deals

.* If you don't have their email address or home address, collect this info and upload all contact info to a CRM so that you can systematically remain in contact throughout the year.Best of luck to you moving forward!

Those will be mostly investor owned, and it often doesn't look all that great, because no one cares....the tenants don't care, the owners don't care and when no one cares....it often looks rougher....more cars, more trash, more weeds, more high grass, more homes that need paint, more untrimmed landscaping, etc.Not easy to do, but you can also look at the tax records....look at mailing address vs property address. 

Then, I would start making the repairs, addressing the most urgent matters first. 

She skipped out without leaving a forwarding address although she is self employed and we seem to have her correct P.O. box address for her and her business(business does not have a physical location). 

They either want the house or they don't...any issues about that should have been addressed much earlier in the process.

You want to address problems head on.Keep in mind that extra basement storage is of value to tenants.

You can skip trace to find things like phone numbers or non occupied mailing addresses.