Timeshares are for all intents and purposes are unsecured debt. Sure, there is a physical property attached, but it's valuation and lack of liquidity make it a real tough debt to settle if a person needs to file bankruptcy, thus it's looked at by many financial institutions as unsecured.
There are varying opinions on financing and then financing against your home. Personally, I don't have an issue with financing, as the outlay of the finance charges are small compared to the total outlay of owning (it really doesn't move the dial that much in terms of your savings over hotel rates). That said, I think placing a debt on your home for a timeshare is a little more risky as it then becomes linked to your home, which means if you default, you don't risk your timeshare ownership, you risk your home.