So what would be a safe way to have that conversation or would it be ok to say that, "We've received notice of smells coming from your unit?"  

These are my numbers going in each unit 525 (seeing rent in area go for 730)Sale Price$75,000.00Down Payment25%APR %%5%Closing Cost Repair Cost$2,500.00Income InfoMonthlyAnualRent$1,050.00$1,050.00$12,600.00Additional Unit$0.00Additional Income0Total Income$1,050.00$1,050.00$12,600.00ExpensesMonthlyAnualMortgage$294.44$294.44$3,533.34Property MGMT10%$105.00$1,260.00Vaccancy7%$73.50$882.00Repair8%$84.00$1,008.00Capex10%$105.00$1,260.00Utilites / MO$0.00Tax / Yr$2,900.00$241.67$2,900.00Insurance / YR$876.00$73.00$876.00Other$0.00Total Expenses$977 $11,719.34Total Cash Invested$21,250NOI / YR$880.66Monthly Cash$73.39Per DoorCash on Cash4.14%$36.69Potential number after renovations.  675/unit (safe numbers)Sale Price$75,000.00Down Payment25%APR %%5%Closing Cost Repair Cost$12,500.00Income InfoMonthlyAnualRent$1,350.00$1,350.00$16,200.00Additional Unit$0.00Additional Income0Total Income$1,350.00$1,350.00$16,200.00ExpensesMonthlyAnualMortgage$294.44$294.44$3,533.34Property MGMT10%$135.00$1,620.00Vaccancy7%$94.50$1,134.00Repair8%$108.00$1,296.00Capex10%$135.00$1,620.00Utilites / MO$0.00Tax / Yr$2,900.00$241.67$2,900.00Insurance / YR$876.00$73.00$876.00Other$0.00Total Expenses$1,082 $12,979.34Total Cash Invested$31,250NOI / YR$3,220.66Monthly Cash$268.39Per DoorCash on Cash10.31%$134.19Any input would be great!

I was considering only using 25% of my equity to be safe.

One of my criteria will be to only purchase in reasonable to cheap property tax areas but I also want to buy in areas that are safe and have decent school districts. 

Generally speaking leaving the money under the mattress is safe but it would not move you forward financially. 

But I feel that is more reason to play it safe. 

It’s also relatively safe if you know what you are doing and can also be quite social.

I'm looking for any advice on what techniques or aps you guys use to keep track of rehab expenses, milage, etc.

Often, they’ll pay for knowledge and education about a particular technique or strategy, but do not have a fundamental understanding of the real estate business, investment, processes, and legalities.

I don't want to pay for a new unit when its nothing but capacitor or a thermostat, or have a short service life capacitor installed so the Tech can get a quick callback for extra work (not all Techs are top notch in diagnosis).If you intend to learn to service your own A/C units on the fly as they go down, I'd say that's probably a rather big learning curve, and will require some specialized equipment and training on how to safely do it.The rent or buy decision aside, it's best to have a couple of experienced reliable A/C techs at your disposal.