Did the contractor pull permits for the pluming and electrical work? 

To put the icing on the cake, I added a signature line for myself and her roommate (who is actually on their lease) to sign saying that he and I agree they violated the lease on all counts and that he agrees to vacate in within the time permitted.

I expect the place to be clean but I don't expect the extras (chocolates, flowers, wine if permitted by law, etc). 

I've listed my high level outline below, and welcome any feedback.1 - obtain all building permits for the property - understand what's legal and what's not2 - talk to the city development person to see whether I can legalize the current illegal units and bring it to code, or if I'll have to remove it3 - after understanding what needs to be done with the property, talk to a home inspector to identify which units are in compliance and what's not (also get all the standard inspection items)4 - work with a general contractor to get a $ quote for necessary jobs on the property5 - bake those numbers into analysis to determine whether to buy6 - discuss property details with lender and get an appraiser's input7 - submit offer after passing all criteriasAs a first time home buyer, what else have I missed?

I understand there are plenty of owners who will turn a single-fam dwelling into 2 or more units without the proper permits or zoning since that is expensive and raises taxes.

First review your landlord tenant laws for your state.I'd go over in depth the language, even if it's only on  notebook paper of thier rental lease / agreement... it has some terms that you should be able to really enforce,, if it's not stated on that paper that a sublease is permitted then "GOLDEN TICKET" .. you have cause (in my view) to file proper notice of lease violation and get them out.To have a attorney to review this is SMART money spent..

If they say no, then you need to ask them if having the property under contract would permit you access to that, if they say no again, then you need to ask about filing a freedom of information act request.

Are there any laws that that permits landlord to view the results of the screening?

appreciate your post....I have a few questionsa) Builders fee excludes costs of permits, design and engineering, appraisal ....right??

I think that they are the scammers , I was literally gone for 2 days , the next door neighbor saw them but didn't saw anything they did tell me it was 4am tho , so I know they are the scammers, I have a permit for some electrical work so other than cutting the power I'm a loss , I think I'm just going to show up with the police at 7am and cut the power and go from there