Typing out all the possibilities & explaining the combination lease back & 1031 would be arduous .In a nutshell, for an effective solution you need to calculate her gain & then brainstorm solutions to solve the sellers situation.

I have ten rental units with a combination of SFH and duplexes. 

This again depends on the city.To bring the unit into compliance down here you would most likely have to combine two of the units as the planning/zoning, bldg department, and maybe fire department (all where applicable, will depend on the city) dictate.

But with your (combined) income, factoring in deprectiation, in all good reality you won't owe anything in addition to what was already withheld by your employers.Obviously, the above is by no means tax advice nor intended to be tax advice.

In VA, property management isn't a licensed function, but being a leasing agent is. 

Investors who really want to sell, but are not quite sure what they want to reinvest in and/or do not want to go out of state, can look at a variety of other investment options, including:Delaware Statutory Trusts (DSTs)Tenant-In-Common Investment Properties (TIC)upREITs (combination of a 1031 Exchange and a 721 contribution into a REIT)Net Lease Property (NNN)These other options have pros and cons just like any other investment solution, so you should always meet with your legal and tax advisors to review your options before proceeding.

Good area, great schools.It is fully functional.

I was wondering is there any way to do a creative deal combining 'subject-to', seller financing, and a conventional loan?

Combine this with all of the other great approaches to real estate here on Bigger Pockets.Just got off the phone with a homeowner in Oakland that was exploring two options to finance $14k in home improvements. $14k subordinate lien @ 8%.Cash out refinance to pay for the $14k.

I have 6 other SFR's that are doing well with cash flow and looking for one or two more for a 1031 this summer to combine with a DST (somewhat like your REIT suggestion) for the rest.