We have put cement backer board up in the bathroom and plan to tile over it later. Can we paint it first until we have the time and money to tile it?

NO.

Jaz

I don't see why not if you use Epoxy paint and scuff up with sanding before tileing.

Epoxy paint is expensive. i.e. Product Listing ..Epoxy paints (http://www.king-cart.com/cgi-bin/cart.cgi?store=epoxy&product=..Epoxy+paints&exact_match=exact)

I agree with jaz... no