A possible exception to the 121 rule is a job related move. 

It must be your primary residence but their is no rule saying you can not sleep over at your significant other place occasionally.Every aspect of investing has a measurement of risk ;)

See the following to learn more about IRA prohibited transaction rules. https://www.irs.gov/retirement-plans/retirement-pl...

@Dillyn Davidson Saurdiff there are special rules.

It calculates cash flow, ROI, and the 50% rule. 

Is there a universal/rule of thumb to help estimate this?

.: $60.00Management @ 10%: $380.00 P&I (30 yr, 4.5% estimate): $871.50Property Taxes: $220.00***Total Monthly Cashflow using 50% Rule: $1028.50

These loans are available for 1-4 unit properties as well and are quite common for those with income restrictions since they consider the deal itself more than personal financials.

Or, if you don't want to proactively support the rule, just wait until they contact you. 

Now I am doing this by hand (figure its good to get the practice) but no property that I know of (correct me if I am wrong) will rent for 3-6k a month (using the 1 or 2% rule to screen properties).