If so, have them put together some comps off the MLS for you where the subject property is located.If not, you can try the town assessors office as mentioned above.Get concrete numbers though before proceeding.

I know people perform these transaction sans Realtors, but I have heard a ton of different opinions on the subject. 

I understand the basic principles of subject-to, lease options and seller financing and I was curious if there's harm in asking the owner (based on their selling situation) if they'll consider a subject-to, lease option etc.?

You could also do a subject to; often you may not need to put any money down to control the deal.There are a lot of great post here on BP and highly recommend you understand all of these options further.

Your losses on the rental from schedule E will go to offset ordinary income (subject to certain ceilings based on AGI).

Very little experience other than working with a GC in building a custom home, but enjoyed that very much and looking to diversity with some residential investments.

Very little experience other than working with a GC in building a custom home, but enjoyed that very much and looking to diversity with some residential investments.

I would get it under contract with $3K net to him subject to you negotiating an acceptable number to the bank and any other lien holders.

Your explanation is a little confusing but I think your referring to a Subject To transaction.

A great book to read on this subject is, "the abc's of real estate investing" by Ken McElroy.This process has helped me identify a bad deal much quicker so I can move onto finding the very rare Great Deals!