Typically, RS3 permits SFHs and two-flats, by right.

Permiting will be stricter I imagine. 

And always have reserves to handle any unexpected issues.

Possibly already permitted outbuildings that already have plumbing such as workshops, offices, etc might be able to be converted to an ADU at a cost that does not result in the cost being more than the value added.Building an ADU is a lot of work and can be a slow process.  

The city already had a STR permit in place.Our permit will cost us about $500 per year.

The tenant has a roach issue, even though my building has a monthly exterminator service.

There are a lot of market-specific issues you'll have to grapple with and also, there are plenty of landmines in MFR on its own in CT that you'll have to be ready for, in addition to the nuances and complexities of developing something like this.

Better than underground homes which have issues with moisture etc.

Their permit will not be transferable when they sell though, according to the draft plan.

Developers will not be able to get these bonus building permits without providing such TDR credits.