Alex, good luck on your journey to start wholesaling. I would encourage you to become familiar with all areas of Orlando because each area will can produce different product. I was a wholesaler in Orlando for 7 or 8 years, I made good money and learned a ton. You will make a lot of contacts that can lead to other opportunities, so with that in mind, be sure to deal honestly with people.
To get started, the fastest way is to market other peoples properties. Instant inventory will give you a location to start working. To gain access you may want to call off of other peoples bandit signs and go to the local real estate investment meeting. I believe the local meeting is this Wednesday at Edgewater High school and the name of the group is Central Florida Realty Investors (CFRI) http://www.cfri.net/default.aspx.
Once you gain access to a list of wholesale properties, go look at all of the houses, even if one goes pending. Once you look at the house, drive the neighborhood and look at other houses in the neighborhood, this is called "driving for dollars." You are looking for two kinds of opportunities, other houses that are being neglected and may be in need of a letter and houses that are being remodeled, which would be an ideal spot to stop and possible pick up a new investor. When you are driving around, you can write addresses down on a note pad, then transfer them to a spreadsheet and conduct a mail merge, or you can use an app to record the address and either send the letter with the click of a button or do your own mail merge.
If you want to do a mass mailer, I would use a service like real quest to pull the leads.
I never gave the sellers a non-refundable deposit when I was purchasing off MLS, from a letter or sticker, however, I always took a non-refundable deposit from every buyer. If the buyer bailed and I was able to resell the house, I usually gave the money back. Try to make it a point to never cancel on contract, even if it means making no money. Unless you made a really bad buy (it will happen) and you have no way to close on the house, its best to follow through to the best of your ability.