For full timing you might need to consider these options and are they available on the trailer that you're looking at:
1) Dual Pane Windows (that are tinted)
2) Heated Enclosed Holding Tanks (Fresh, Grey & Black)
3) A Fantastic Fan To Pull Old Air Out of the unit
4) Winter bypass valve
5) The use of PEX Plumbing lines. Pex is a better material used on higher end trailers (very important)
6) Enclosed underbelly
7) Vent & hatch snapping covers
These are all important and VERY NECESSARY in colder climates, even in Northern California!!
You might want to look at Lance Travel Trailers, as they're all 4 Season Trailers (except for their baby trailer, the 1575) You might be able to find a previously owned Lance and that would help out with the depreciation, etc.
Here is a Link:
Lance Travel Trailers