Why only do real estate? Why not do landing pages for simple physical products, enterprise SaaS software or mobile apps. Real question though what do people actually use for the above ?
Real estate is a good target because developers will frequently crank out a new website for each new development, which will be used for six months or a year until the units are sold, then mothballed. The requirements of such a site are well defined and simple, and the short lifespan means there's no point in spending much money on them. Still, they have to look like money.
Source: developed real estate websites for several years.
Apart from Kluny's points, focusing on a single niche makes things easier in the beginning. It's better to be THE landing page builder for Real Estate than one among hundreds of general landing page builders.
I'm hoping to expand this to other markets too. Everyone needs fast, beautiful landing pages. Real estate is a market i'm intimate with, so i'd figure its a good start
Source: developed real estate websites for several years.