It has a huge backyard,and I can build another 900 sq ft 2 bedroom unit which I think will add $100k to the value of the property for a total of $300k.But there are no comparables, and my realtor could only give me duplexes which were only about $250k.My question is should I build this second unit rather than look for another "very hard to find now" flip?

I agree with @J Scott and @Manolo D. what anyone can tell you online or in a book is how that person goes about coming up with estimates.

Simple online mate. 

The trustee will usually be instructed to bid in on behalf of the lien holder the total of amount of the principal, interest owed, late fees and legal fees, as well as any other legitimate fees incurred by the lender.

It's funny because the online course has actually covered this question in classes since I originally posted, so I was just thinking ahead I guess.  

There are online directories where you can look up a prisoner's location (you'll have to know whether they're in federal or state prison) and then you can send them a letter.

If still no one is taking them, they will post them online (such as LoopNet).

., then foreign qualified in RI (Foreign LLCs still must have a Registered Agent).Additionally, forming an LLC in Mass. costs $500 by mail of $520 online.

Monthly mortgage payment for 30 years with 4.5% interest rate is about $1,400 (total monthly). 

missouri or something buying $30k houses its totally different.