Zillow.com can give you pretty accurate estimates.
As per my personal knowledge:
Areas around the University of Memphis can range from 400 for a 1 bed to 600 for a 2-3 bed.
38125 rates are usually 750-900 for a 2-3 bed. Any germantown area will be pricy ranging from 1200-1600 for a 3-4 bedroom (38138 and 38139). Collierville can also be quite pricy as these are sought after areas due to demand of the school district.
Many 'Memphis' areas downtown can also be quite expensive ranging all the way up to 1000 for even a 1 bed if you're near the river.
Areas around airways and american way/perkins ave can be pretty cheap such as a 3 bed for around 500.
Let me know if you have any other questions.
First National Realty