I've had a few requests for further information and discussion on this topic, so I've done a little more number crunching and will share the results.
When determining whether or not to replace lower level buildings vs. hood expansion, there are a few variables that one needs to consider, mainly play style and are you a short term, or long term goal player...
Here's a simple way formula that I would recommend to determine what would be the most efficient decision to make on this subject. Remember that all buildings one is considering selling have a potential earning that would be it's income at lvl. 10. This is the # that should be used when determining a buildings worth.
1. Determine how many squares of real estate your next expansion will give you
2. Figure out how much each square will cost, based on the total expansion cost / # of squares
3. From here, determine how much income you are getting from each square of the building in question
4. Now you can determine how long that building would need to pay for the upgrade.
Tattoo Parlor lvl. 10 = $18,750/day
@ 16 squares, this would be $1171.88 per square, per day
If my next expansion is $2.4 million, and provides 192 squares, then is costs $12,500/square.
At this rate, the Lvl. 10 Tattoo Parlor would take 10.67 days to pay for the space it's taking up.
As the cost of expansions get larger, buildings values will go down substantially. Here's a short list of some of the earlier buildings return values, based on the $2.4 million expansion @ 192 squares:
Tattoo Parlor = $1171 / day / square = 10.67 days
Pawn Shop = $609 / day / square = 20.52 days
Gun Shop = $703.13 / day / square = 17.78 days
Souvenir = $625 / day / square = 20 days
Deli = $562.50 / day / square = 22.22 days
Diner = $625 / day / square = 20 days
You can take the $ / day / square numbers and apply it to your own next expansion to figure out what the return is, but as you can see, at this expansion, all but the Pawn Shop have the potential to be more valuable than the expansion. I would weigh the # of days for each building vs the # of day it would take to save up for the expansion, and go from there.
At the earlier levels, I can't justify getting rid of most of these buildings unless I decide to never upgrade them to level 10. If you don't, you can adjust the $ / day / square with the appropriate #'s for the level you are at for each building, or the max level you plan on taking it to, and go from there.
Remember, don't ever get rid of a building until you have the cash, and are ready to replace it with something better!!!