All I can tell you is what I do which is through my payroll company. I use Paychex and they have a "Pay by Pay" option for WC. There is a deduction each time you process payroll. I know ADP also has the same option.
I have found, as well as my friends, that quickbooks is the best bet for new companies. You can pay as you go, instead of the huge outlay from the get go. Also with the pay as you go you don't have to worry about the huge outlay at the end if things *hopefully* go great and your payroll is more than you anticipated.
Quickbooks is by Intuit, you can find more information on their website.
#1) WC rates in florida are set by the state. All the companies will charge you the same rate.
#2) I called quickbooks a year ago and they said they don't write construction policies in FL (probably because it is set by the state).
#3) Absolute Pay Trust ( http://www.absolutepaytrust.com/ ) is who I went with. They are in Sarasota. They have an option to make your workers comp policy 'pay as you go' with payroll. I couldn't be more satisfied with them. I would strongly encourage you to call them.
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