Like was mentioned, do you have a rough budget in mind?
With the economy as it is, you might be able to find some nice used industrial/rental diesel generators for cheap.
A quick search at United Rentals site shows several in the 19-30 kW range around $7-8,000.
http://ur.rousesales.com/EquipmentItem.aspx?id=3391976
But, with diesel you need a new fuel storage tank, block heater (or glow plugs), etc.
Good luck.
Her budget is $10k, but if I give up some things we can stretch up to $15k"ish". $20k if we go to Ramen noodles for the rest of 2010.