A good place to look for rentals would be Craigs List. Be careful you are truly dealing with an owner and never send money to an owner in exchange for keys, no matter how wonderful their story sounds. Legitimate property owners also advertise on Craigs List, but so do the scam artists - if something sounds to good to be true, it most likely is.
A good property manager can also help find properties for your specific needs. There are a couple in Sarasota I would recommend, as they have the largest inventory of rental property. One is Stringer Management and the next is Casey Management.
Good luck. I have owned German Shepherds myself in the past and they were all well behaved. Unfortunately for you, insurance companies rate their troublesome breeds by the number of claims received overall for that breed. A Shepherd is just a higher risk than say a Golden Retriever.
I hope my answer helps you.
Xena Vallone, Broker Owner, ABR, SFR
Xena Vallone Realty, Inc.
3562-A South Osprey Ave.
Sarasota, FL 34239
941-224-5950 (cell) / 941-706-1717 (office) http://www.XenaValloneRealty.com