While it's true that you can walk to many places in Venice, if you are vacationing, you are either driving to the vacation house or at some point, you'll want a car to see something other than Venice.I would think that a parking space would add/subtract a couple of hundred thousand dollars to the price.

I would subtract the $1200 from the sale of the price.

Obviously I need to subtract mortgage, interest, taxes and insurance from the $3000, but how do I estimate additional costs that I will have to pay?  

If you are going to live there then subtract out that room expense and your portion of utilities.  

Even with those 3 subtractions, we still filled THREE 30 yard dumpsters.Simultaneous to that project we also did another where the deceased owner had only lived there 10 years, so it only required TWO 30 yard dumpsters.We just finished two more acquisitions one required TWO 30 yard dumpsters and another which was a mobile home required THREE 30 yard dumpsters.The accumulation of stuff and the lack of desire to move and change is keeping many seniors in their homes until they have to leave. 

A house built in 1960 can use the plus/minus of 20 and include 1940 to 1980d) Try to find same bedroom count. e) Then add/subtract adjustments for bathrooms (5k for one less/more bathroom, etc), garage (10 to 15k for garage/no garage).Be sure to stay in the same subdivision first.

Then subtract your profit and any other out of pocket costs and there is your offer to the property owner. 

.$65,000 financed for 30 years at 5.75% = P&I of $379.32 a month.If income is $1,100 a month... after 50% expenses you're at $550 a month... subtracting P&I is 170.68 a month.Unless there are a bunch of utilities tied into this deal, sounds like an absolute no brainer.Also, some of your numbers make no sense. 

Is that amount subtracted from the basis, or is that money allocated proportionally to each item in the closing costs it covered?

Subtract the loan of $87,500 and you need to bring $7600.As you hold, you'll make monthly payments of $1093.75.