However, that nice return was only going to last so long, as a bunch of cap-ex issues were going to rear their ugly head sooner than later and the price was threatening to be high (though it would have still been a good cash-flow investment had I held it, appreciation was uncertain).

That may make sense but I am uncertain. 

If it was a 10 year strategy, it was probably in the 0-10% annual realm.If someone is uncertain in the market, a longer term hold mitigates some of that risk.

(And I now need to post elsewhere, since our Tenants are potentially litigious types, so we are uncertain if we want to go without a Manager!  

This is standard procedure for most builders these days and is very helpful for communication, scheduling and budget.Remember its all about relationships and as the developer you are the leader so its up to you to provide clear direction in no uncertain terms exactly what you expect and when then measure that performance and hold the team accountable to the goal in a way that is positive and encourages the results you're after. 

But WA is looking to pass legislation similar to Oregon's that is much friendlier towards tenants.

If the program is revoked, any de legislation has been for new borrowers only.

You should considered talking to an architect who has done ADU work in the area to knock out some of the easier questions that are explicitly stated in CA legislation. 

I thought I remember hearing, in the last year or two, about some massive state-wide rent control legislation in Oregon.

I second @Kenneth Garrett regarding online resources, I use Rentometer, but more recently something else has helped me too: I joined a FB group of renters/sublets to find out what a room rental was worth, and based on that I was able to rent out my spare bedroom for 3 months during the legislative session -- $900 a month!