It sounds like you have a solid system with clear communication on extensions and vacancy openings.

If I wanted to get more involved and spend more time on investing (like if I was 20 years or more younger) I would make extensive use of options.

One of the things many say is that you must intend to perform on a purchase agreement or it could be fraud which is BS.

Periodic 1031 exchanges when appreciation stalls out, or performance goes down, or trapped equity is costing you return are all great strategic moves.

That market from what I can see on the few trips I made to perform due diligence is really robust and such a pretty area I can see the attraction for those working in Tech or govmit in DC. 

Books are important to maintain because it keeps track of the performance of the partnership not only for one year but over several years.Partners normally have the right to inspect the books.Will the accountant you work with either maintain the books for you or help you make sure its done correctly?

I agree with @Chris Seveney that a performing note would be a very good starting point.

And a little skepticism that the market would continue to grow at 5% or more on average (it's been ~7% average for the 8 years I've lived here)@Dave Foster I filled out the BP spreadsheet here for the sell or rent decision, and similar to you advice, selling and investing the profits in index funds performs only slightly below being a DIY landlord, making that seem an attractive option. 

This process is extensive, requiring community engagement and approval from the City Planning Commission and City Council.Given the predominance of multifamily residential properties in your area, there may be a precedent for such developments.

Small multifamily, up to 4 units (at least to start), then graduate into larger investments as your portfolio performs positively.