For our ADU (garage conversion), I am handling the design/engineering and then selecting a final contractor once its permitted and ready to go. 

I'm a construction management consultant (so similar to engineering) and investor/agent in the Boston area so I get the need to want/need to stay local.

Overcrowding can strain plumbing, electrical systems, and air conditioning, leading to expensive maintenance issues.

Without electric you can not heat the unit.

I think the engineering issues on them have been resolved.I've used a number of different brands (lower price point) and haven't had issues with any of them.

:)As for LTR rental terms, usually we sign a 1 year lease where tenants are expected to pay Electric and Gas if applicable, while the owner typically pays water/sewer/trash with the city. 

did half the flip work, sold with new walls and new electric/plumbing.

It's a big money maker for architects, engineers, and contractors, but not a huge opportunity for investors, nor should it be. 

On the other hand, pros include increased cash flow, engineer-based data for the clients CPA, audit protection (with the right firm) and the ability to deflect that recapture fee with a 1031 transaction.

2) Electrical: Because we have no heat, we've been using two space heaters.