The formula for homes is 2+(0.2*donorLevel), so a $10 donation will result in 4 homes total. (This is given in discrete jumps for each donor level, $30 doesn't give you 8 homes for example)
So yes, it includes the 2 base homes (in your case home and xp) as /home bed isn't counted towards your home limit. The number of homes it says on the donation page is the total number of homes you'll have access to, excluding your bed. Hope that clarifies it.
We're always open to suggestions for donor perks though.