Turning my primary residence into a rental

[Joshua A Blake]

I am about to refinance my primary residence with the intention of pulling out $80,000 in equity to purchase rental properties.  We already have an agreed offer on a home for $30,900 cash and we intend to put about $15,000 into it.  Rent will be $600 per month, total expenses about $300 per month.  Just yesterday I had a close family friend tell me they were searching for ranch style home in my home town with lake access.  My primary residence is exactly what they are looking for.  I am considering offering them a slightly high rent rate of $3,000 per month, and I will move.  I expect the home to be valued at $285,000 when I refinance.  I want to rent to make this work, but I am afraid I won't be able to get financing to buy another home.  How long does rent have to be collected for the banks to consider it income?  My income without the rent considered is going to leave me unable to buy a home to live in, or at least that's what I'm afraid of.  Any suggestions on how to make this work?