(Assuming the remained of the roof is in good condition and not too old.)

My rule of thumb for rehab costs is try to gain at least $2 value increase for every $1 spent on labor and materials.

Some towns have brutal rent control ordinances that can prevent you from increasing your annual rents. 

ERGO you are in foreclosure in the first place.GFC meltdown saw values drop 20 to over 60% in certain markets  .. your 70% LTV loan was underwater right out of the gate.So to answer your questions.In General... you have a foreclsoureyour value is 10% less than it was when you made the loan.. reason flipper butchered the job ... and again depending on state it could take 1 to 3 years to actually foreclose and of course your not getting any payments.. so your interest is wiped out. your cost of doing the foreclosure again state specific.. and I have never met a defaulted borrower that paid the property tax's  ( and again state specific how bad this will be).. you have selling costs usually 8% and you normally have to spend money getting the home marketable I have never met a defaulted borrower who left a home in perfect shape.So you add 10% market devaluation  8% for sales costs.. 3% for foreclosure costs.. 2% for back taxforce placed insurance and utls.. and depending on the condition of the home 5 to 10% for rehab .. you can see how this eats into your 30%  .. then take states Like were i live and properly filed mechanics liens are super liens they jump ahead of your mortgage.. this can be thousands up to 100 thousands if your flipper totally screwed the subs. 

But Patrice B is right in the fact that there are many factors going into an assessment of value like # of bedrooms, baths, sq ft, condition, age, location, etc.

@Alex PerezYou can get a 30 year fixed interest rate loan on sub $50k properties, with conventional financing, as long as the properties are in livable condition.

Is it true that you can increase the price of a home that is offered with seller financing so perhaps this amount offsets the discounted payoff offered by the note buyer or at least this increase may pay all or some of the Realtor's commission?

It appears the units are below market, however with some cosmetic repairs and perhaps some capex's I feel I could increase the rent by at minimum (based on local comps) 68%.I would offer 85% of list and estimated $20,000 in repairs/upgrades (this is probably a generous estimate - the property appears to be in good shape, basically needs a face lift).With all these figures, including the 50% rule, financing with 20% down @ 3.5%, I come out to a profit of $262 per unit and a cash-on-cash return of 9.53%.So, does this seems reasonable?

My question though is that if the most recent property tax is based on the previous sale price, if your purchase price increases dramatically then wouldn't you get a huge spike in taxes?

As you build your portfolio (you have to buy #1 before you buy #2) your income will increase, your net worth will increase, and there are always options to refi and take some cash out of performing investments to help secure the next deal.