I am now in need for 50 alarms.I am looking for an alarm that fits the following criteria: 1) 10 year battery (so tenants don't take it down when beeps for low battery, 2) Photoelectronic and not Ionization. 

That way you could make sure the plumbing fixtures aren't leaking, the air filters are changed and smoke alarm batteries are changed.

We use Rent Manager, which has a great accounting module, but it's expensive.

However, just like anywhere you are in the country, there are going to be some areas, that are simply not a favorable space (East Cleveland, Cleveland Proper (except: Tremont, Ohio City, University Circle, Gordon Square, Duck Island, Battery Park, Detroit Shoreway and a few more notable spaces)) moving on, the remaining eastern communities will give you settings featuring lower-middle-upper middle class, as well as premium upper class communities, but they do not seem to be on your radar anyway.

The middle unit has smoke detectors without batteries.

@Andrew M.Well, you will definitely have to have all the smoke detectors to be hard-wired (with battery-backup)...and they need to be wired so that if one goes off upstairs, then the others go off as well. 

This is what I'm thinking I would use: http://kithaus.com/modules/k6/In San Diego I'll need the right zoning at at least a 3000 sf lot for the areas I'm looking at (North Park, Normal Heights, City Heights).

Instead of spending $50 on a new battery, I went ahead and bought the Dewalt impact/drill combo pack and couldn’t be happier.5) Water heaters can also be saved for a last minute turn on.

Runs on a 18V drill battery and you can knock out a lot of trim on a single charge. 

DJ,In any investment scenario, whether for buy and hold or flip, we always put in a drain tile system with a battery backup.