The biggest downside to assumptions is that the leverage might not be favorable if you're buying the property for a significantly higher price than the seller did.

Just though I would let you know that there are many down side of investing in real estate mostly do to tenants not paying rent or repairs so adjust your numbers accordingly. 

The downside is that they can leave at anytime with a 30 day notice.To determine the amount of rent to charge, you really need to do a rental comparable analysis.

Another down side is you need to wait a full 5 years until the monthly mortgage insurance is removed, and only if you are at 22% equity based on original appraisal.

The downside is, often with very long term tenants, you cannot even incrementally bump rent, at least in the stories I hear.  

The upside is the cash flow- about a thousand a month- on the properties but the downside is the area property values have been declining about 7% a year since 2006 and the market has showed no signs of turning.

Wow, thanks for the quick replies everyone :) So, what is the downside of upgrading the service and running new wiring but leaving the knob and tube wiring in place in the walls instead of fishing it all out?

But the upside, to me, seems to more than outweigh the downside.

But the inventory in St Petersburg isn't great.Tampa seems to have nicer places for the same price, I'm sure there's a downside.  

The only downside I've found is you have to have a wall mounted unit in each room.