That depends on a number of factors: The condition of the home, the park generally, and the ground rent or land lease.
The first factor is fairly obvious. What condition is it in? How are the appliances? How's the HVAC unit? What's the condition of the bathroom (or bathrooms)?
The second is the park generally. Sort of like considering comps when buying a home, but more broad-based. You certainly should consider any comps. Most mobile homes are privately sold, so it can be more difficult. Still, if the park's large enough, just drive around and find other units with the same number of bedrooms (and whether it's a single-wide or double-wide) and see what they're going for. But some parks are really quite nice. Others aren't. That affects the price, too.
The third is the land lease. And that cuts both ways. A high land lease can mean the park is a really nice one with lots of amenities. There's one near where I am with a real high ground rent, but it's a gated community with a club house, swimming pool, basketball courts, and more. You just have to figure out if you're getting a decent value there, and how the park management is.
Tip: If you're buying with cash, sellers in mobile home parks often are VERY flexible with price. Especially if they've been trying to sell for a few months. In many cases, if I found one around here priced at $7,000, I could probably buy it for $5,000 or less. You should be able to do the same thing.
So, without knowing what it's worth, I'd still say that if it's in decent condition (make sure you have the HVAC, appliances, roof, and plumbing checked), if the ground rent isn't outrageous, if the community itself is OK (not great, but OK), and you can buy it for $5,000 or so, it's probably a decent deal.