Been there...done that ;)
Workamping for site is the better option in my opinion. Usually requires 20-24 hours a week combined...most of our jobs were 2 days a week. We found these types of hosting to be less stressful and more laid back (and fun).
As someone already mentioned, when hosting for pay the reward is not worth it...after you do the math it's usually much less than $5/hr. Most will expect you to work all hours assigned (40+)...more stress, less fun.
We've done Amazon and enjoyed it, but the season is short, Sep-Dec, and only certain locations...if you have to drive a long ways to get there (and back) it will take a good chunk of your paycheck...at least until they decide to raise the hourly rate. They still pay the same as in 2009 and everything costs much more now. But if your close to one of the locations where they hire CamperForce then it might be a good option.
Parks generally cost $400/mo. and up depending on the cost of living in the area you choose. I have seen a few that have 6 month and yearly rates that could save you a little. Keep in mind that most long term spaces do not include electric. This is why a lot of folks do hosting...no rent and free utilities.
Like I tell people, travel and lodging are the 2 biggest expenses when full-timing. If you can host for 2 days a week for a free site then you eliminate one of the 2 big ticket items.
Of course you will still have all the normal expenses...medical, insurance, vehicle registrations, etc. And don't forget Uncle Sam! You will need an mail address that provides you with a legal residence. We went with Escapees and became residents of Texas, but there are others that provide the same service.
Best advice, keep asking questions here on the forum. There are plenty of knowledgeable folks here who have been through the process already and will share that knowledge with you.
Good luck on your dream.
Dan