@Brian Lesko
Here's the number one thing I would check, the capitalization rate. IF total gross rent is $1050/month, that means a yearly gross of $12,600. What are the yearly taxes? Is the duplex in Washington or Allegheny County? Check that. Check that like a hawk.
For a purchase price of $69,000, you're going to need the net operating income to be $6900 to hit a cap rate of 10%, which is the minimum rate I would accept for a duplex buy way out in a place like McDonald. To hit a cap rate of 15%, which I would consider a sweet duplex deal, that NOI would have to be at $10,350. I don't think that's possible in this case.
Figure out the taxes and expenses and come back with the cap rate. If it's below 10%, present the numbers to the seller and start squeezing them down on the purchase price.
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You're buying a duplex from an older couple who wants out of the game. You should expect that the building is not in good shape and there are many deferred maintenance issues. You correctly identified the roof as something to look at carefully. There are other things to watch for, maintenance issues that will push your NOI down to zero and into negative territory in a hurry. Here's some building basics for your inspection tonight.
1. How old is the building?
2. Is the electricity knob-and-tube, rag wire, or updated modern wiring? If the wiring has been updated, get yourself a cheap electrical plug tester if you don't have one already. Sperry makes a cheap one. Plug it into all the existing three-prong outlets and look for incorrectly wired updates, especially open grounds.
3. Insist on a sewer inspection. If it's an older building surrounded now or in the past by mature trees with serious root systems, there's a chance the main sewer line to the stretet is leaking. Get a plumber with a fiber optic scope to run the scope through the sewer line.
4. Check the gutters and look for leaks. Check the downspouts.
5. Is the basement wet? Look for telltale white spots, efflorescence on the lower part of the basement walls that commonly indicate the regular intrusion of water. They probably won't have a sump pump in there, but if there is one, look extra-carefully for signs of intrusion a good distance from the sump pit.
6. Keep your eyes peeled for deferred maintenance issues on the concrete work, stairs, landings, slabs.
7. Check the water piping. Is it steel or copper? Steel is bad and is probably already causing issues in water flow and pressure in the duplex.
8. Check the bathrooms. Make absolutely sure there's a modern tub in each of the apartments and the tub surround runs at least five feet up the wall. Often, the bathrooms in these duplexes in this area need serious updating. Make sure the tub areas don't look like this. This was an over-under duplex in Munhall after I stripped the wallpaper and the green plastic film the former owners had superglued to the ceiling to try to keep the plaster together. Note the lath stuck up in the cavities from previous repairs: the guys that rigged the last repair job didn't even carry that out.