How do you calc monthly mortgage expense?

[Julius Dixon]

Hey guys, does anyone know a rule of thumb to use when calcing mortgage payments? Just trying to figure out some assumptions for the model I'm making. FYI I don't know too much about how different credit scores will affect my mortgage payments, so I'd also appreciate some guidance which incorporates high vs. low credit credit scores.) Thanks!

[Justin Fox]

Oh snap.  I don't figure that stuff out myself.  I'll use BankRate or Excel/.Net's PMT, PPMT functions and etc.  

For the .25 and .50% remark, I meant if the current good rate is 3.9% for owner occupied properties, I would calculate my mortgage .25 or .50% higher for investment property, maybe even a whole percent.

I'm not sure how the PMI is actually calculated, I just know I pay an extra $60/mo and you could use that information in your calculation if you planned on doing a down payment less than 20%.

Typically, you're interest rate will be lower the more you put down and/or the shorter the term.  If you buy a home for 120,000 and put 20% down, your mortgage will be calculated off the remaining 96,000 balance.  

Your debt to income ratio will really only affect your eligibility for the loan. I guess you could be forced to do a 30 year loan in order to squeak by if your DTI was too high at a 15 year term.