We have been renting out a home for about 4 years now the first family were kind of a pain and they left things a bit of a mess....the family we have now is wonderful they keep things great. Because we are going to sell that house at some point we provide a weekly gardener, and pool care their rent covers that the mortgage, insurance, propery taxes, and we make a profit.
Talk to your agent about getting all the proper documents and background checks that are legal. If she is your selling agent she should give you honest advise as far as what you can or should expect and how hard or easy it is too sell while you have renters.
Also talk to your financial/tax guy ask how it best benefits you and your situation for selling now or renting first.