Welcome to Fiberglass RV!! Since you are an archeologist, you should be familiar with roughing it and living in limited circumstances and you should do fine with a 13 foot.
I think our rig is number 16 on Frederick's list. If not, it was the same value when we were weighed at Quartzsite last February.
We are two people and our trip this spring was something like 7 weeks + and I could see no reason why we couldn't have gone on indefinitely.
However, that being said, you cannot bring along any weighty hobbies. You have to put your anvil collection in storage!!
We have the dual dining floor plan. My wife sleeps in the aft bed and I sleep in the forward one, which we make into the table daily. You, being single could use either, or get a forward head (restroom).
You live in So Cal. Hop over to Temecula and take a look at the Trilliums,
Only you know your situation vis a vis your ability to work on a used trailer versus your pocketbook to buy a new one. Since it seems your situation is such that you need something soon, I can recommend new. Just tell them I sent you. LOL