an unfurnished 3 bedroom house will cost you anywhere from $1,200 to $2,000 per month, depending on the quality of house.
When I moved to St. Pete, I leased for a year, also with the thought of possibly doing a lease purchase down the road. After living in the house for a few months, I realized that there were so many other possibilities for purchasing that the lease purchase didn't seem appealing any more. Once you get a feel for the city and the different areas of town, you and your family will get a much better idea on where you want to purchase. We do have lots of good inventory.
I hope this helps and I am welcoming you to St. Petersburg.