I guess you're aware that Cuba isn't like, say, Germany, where you arrive at the airport, hop into your rental, and drive from one place to the other.
I'd suggest to hire someone to drive you around. Yes, you can be now getting modern cars (exp Chinese Geely), and renting is possible, but it's still not as easy as in other countries. If you really want to rent it yourself, please note that most rental sides have 30 days in advance reservation. And it's NOT cheap to rent a decent-sized car. Expect around 250$ per day!
My suggestion is you get a driver, or check for alternative transportation (Cuba is definitely possible for a backpacker, but you might not like that, and with one regular sized luggage per person, being spontaneous might be much harder then with a small backpack..)
Thus: Driver, or alternative organized travel altogether. (They will organise stays in Home Stays too that way..)
This is CHEAPER than hiring a rental yourself.
According to
http://www.erlebe-kuba.de/osh/de/htm...ba/0,261,.html the current rates are:
Per day outside Havanna - 1 bis 4 days, per day € 95,00
Per day outside Havanna - 5+ days, per day € 90,00
If you chose a driver to be a bit more flexible, about places to stay, I'd suggest you check out
https://www.homestay.com/cuba - there aren't much hotels outside of the big cities and tourist destinations, and it's much more fun and authentic to stay with local families.