They are very less painful when a  unit goes vacant, especially when not expected and that will happen. 

First, I will say that home owners warranties are a complete pain to deal with.

This is a pain in the butt with hewn lumber because R-13 won't get it done.

Switching now from a peak bull market into a self-directed IRA and investing in SFH rentals from there would benefit you more than the HELOC pain.

Granted, there will be exceptions where a person could hit the jackpot with the 2% rule (there was another thread about people and their success with 2%+ properties).. but the majority of 2%+ properties seem to be pains.

If you do, go ahead and mention that since he may not have even thought of using such services.If he mentions a pain point in his business: something he doesn't enjoy doing, an area that he feels is holding him back etc..see if you can help in that area. 

If your business doesn't do as well as you want it to do in the first year, it may become very stressful psychologically and financially, and it will hurt your chances of success.    

If the units are occupied, I might go with them currently rented you might just keep that money keep coming but I recommend you acquire more units soon as possible to reduce the overall pain that goes with a vacancy. 

Snohomish County is a great area to invest, and the airport at Paine Field will be a major factor.

Roofing is the biggest pain point.