After calculating the principal and interest, taxes, insurance and other fixed expspenses he applies 5% to repairs and maintenance, 5% to vacancy, 5% to capital expenditures,  and 10% to property management. 

A 30 year fixed mortgage is only fixed on the principal and interest portion.

I'm also taking in a small profit each month, which I put additionally towards the principal.

Interest plus Principal), from day one.On the surface it seems like a good idea to only pay Interest if allowed, but, in the long term that only helps your Lender.  

That is probably above 15% total return once taking into appreciation, principal repayment and depreciation/tax benefits - maybe even north of 20%. 

I'm currently living in it and the owner is looking to sell.Property Value - $168K (roughly)Downpayment - $32k (20%)Closing Costs - $4kRent - $1350-$1450 per month (that's what other similar condos in the complex rent for)HOA - $268 per monthProperty Taxes - $170 per monthHome owner insurance - $50 per monthRepairs/maintenance - $70 per monthProperty Management - $120 per month (roughly) Principal and interest - $550 per month (roughly)Is this a deal?

Furthermore, It would be a huge benefit to have a key principal or high net worth individual on your team as you source debt. 

Most homeowners are eligible for this exemption if they own and occupy their property as their principal place of residence.

@Lei Lu are you considering buying a 2nd principal residence and turning the first home into a rental, and growing your portfolio that way?

Pareto Principal.