My mortgage on my primary home is paid in full - no interest to claim. Have 2 vacation homes that do have interest - home and RV. Can I claim both the vacation homes?

It depends.

Mortgage interest is allowed as a deduction on your primary residence and second home only.  

• Per IRS, your primary residence is home where you live most of the year.  IF your vacation home is where you lived the most, you can treat it as your primary home and deduct mortgage interest
• For your 2nd home - you can choose which home -vacation or RV (RV must have cooking, sleeping and toilet facilities to be qualified as a second home) you'd like to deduct.  Per IRS "a second home is a home that you choose to treat as our second home. If you have a second home that you do not hold out for rent or resale to others at any time during the year, you can treat it as a qualified home. You do not have to use the home during the year."

Note: You can deduct property tax on all three properties.