You mention storing the black trailer also. That may be your biggest hurtle.
Getting an RV and setting it up at a year-round RV Park can be doable. Depending on what hotels you currently stay at, it is likely to be more expensive. Figure anywhere from $20-100 per night 365 days per year. That's a minimum of $7,300 just for the site. Electrical may be extra. And remember, that's on the cheap end of nightly rates - which may not equate to a place convenient or practical for you.
If you can get a year-round site, they most always have sewer, electric and water hookups, so that should not be a problem in and of itself.
Finding a year-round site that can also fit your work truck and white trailer may be more difficult. It's possible with a yearly rental and not staying there all the time, you could make an arrangement with the park owners/management to park the trailer on the property but not at your site.
Finding a year-round site to do all that PLUS have a place to store a second trailer is not likely.
Depending on how often you spend the night in San Diego, it may be a better option to find a slightly better hotel to stay at.