Our past clients have utilized this strategy for their first 2-3 small-multifamilies, and just over 3-4 years have 10-12 rentals doors.

We have under 15 doors.

I would sell the properties.4 rental properties over 3 years won't make you much money.Maybe 100 per door per month in cash flow and a matching amount in appreciation.That is $9,600 over a 3 year period assuming you have SFH's.You are improving your ability to make more money in a better position hopefully when you complete your master's degree.You will make that $9,600 working 2 weeks.The sale of the home will hopefully allow you and your wife be stress free for those 3 years helping you make a higher hourly rate.

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases.

I'm a "newer" investor as well but have scaled my portfolio to 10 doors across mostly Detroit and Memphis.

But keep in mind that you are not able to market or select only tenants that do or do not have a voucher.

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases.

I'm based out of the Seattle area but I've built a 10 door portfolio mostly across Memphis and Detroit using a combination of turnkey, BRRRRs and everything in between.

I invested with Open Door Capital 1.5 year ago. 

For us it varies by property - smaller more urban units can be 80,90% Airbnb whereas larger beach houses can be as low as 30% Airbnb but company wide on 65 or so doors last I checked was 40% Airbnb, 30% VRBO, 30% Other (Direct, Marriott, Google, Booking.com, Jetblue/Allegiant Airlines, others).