Make sure it's by an electrical  Outlet.( That could  cost a little)The Engineer cost is still  going to more and  his report will suggest all that I stated plus much  much  more Good luck 

She only pays the electrical bill.

One of my favorite ways is by going to your local plumbing/electrical/building materials supply houses and speaking with the counter person(s). 

Before you submit an offer I would also make sure you know all the additional expenses that you may me overlooking, is it separate metered for water gas and electricity.

I know a lot of people that do concrete work, flooring, sheetrock, plumbing/electrical, cabinets/tops, paint, etc. but I still need to get the units built. 

There are some differences for sure but I don't think they are substantial.3) What laws should I watch out for (for example am I allowed to have the water/electricity be under the tenant's name) - You can put all utilities in the tenant's name, but I would advise keeping water in your name since that utility is a lien on the house itself.

This includes raising a roof, running electrical and sewer, installing a bathroom and kitchen and finishing everything off.

So he took the electric bill, the water bill, and the sewer bill each month and divided them by 15.

Flat roofs, old roof age, old electrical, cast iron plumbing and non impact openings will mean much higher premiums. 

Obviously they require electrical near by.