That one looks fairly beat for the price. I am not up to date on California prices or availability but I would still keep looking honestly.
If you want to convert to camper here is my opinion. BTW, I've done several. I always consider a few things related to resale when shopping because I never keep anything that long.
E250 and E350 both fine for a conversion. Unless you can think of a bout 5 reasons why you think you might need a diesel don't even consider one. They are much more maintenance intensive and also more rare and valuable. Look for a 5.4l or 6.8l (V10). The fuel mileage on the V10 isn't much different than a 5.4l (average of probably 11 mpg vs 13/14). If you aren't going to drive it daily I'd look for a V10. Don't go as small as a 4.6, the only other one available. It's too small for a converted van. The most readily available van out there will be a 5.4l E250/E350.
Look for one with a power cab (power windows, door locks and cruise control). These are features every camper conversion should have. This is only my opinion but I feel strongly about it, especially for resale. Don't sink a lot of money in to a base work van. The creature comforts are worth having on road trips.
I'd look for 2005 or above if considering a V10 to get the 5r110 (5 speed) transmission. It makes the conversion easier and is a stout and wonderful trans. A 5.4l in an E250/E350 really needs at least the better 4r100 trans (instead of the 4r75 base one). This stuff can be found using VIN decoders (and folks here) when shopping.
Don't cave. We're discussing one of the most prevalent vehicles ever made. They are literally everywhere and since the line has been replaced there are more for sale.
Be willing to travel.