@Christopher B. Values can be tough to gauge market to market. They also vary throughout geographic locations as well as time of year. I buy more liberally in late winter/spring to make sure to have inventory for the tax season rush.
That said, guard your cash like a mother bear. Last time I checked, none of the MH investors out there came from CEO positions of Fortune 500 companies with tons of cash in hand...we all worked our tails off to get where we needed to get - and CASH is KING!
Get yourself an option on that home if you like it.
What happens if they don't sell? Can they go to Cali if they don't? Do they have other buyer's? Will they finance some to get to the higher price? Will they owe money if it doesn't sell? Find your leverage point and squeeze it. If you can't get to where you need to be AND have to use cash immediately, it may not be the right home. You've got something that looks decent, but the curb appeal is not great outside and it LOOKS like a $3000 trailer. Keep that in mind as you negotiate. Do you think you're selling that thing for $3500 within a week if you even get them down to $3000 today? And that's just making $500...
The home will need some sort of heating. If it has nothing (what happened to it?) you'll need to throw in a furnace at a minimum. New furnace with install should be ballpark $1200. Used for less, around $600 to $800. I got lucky with my furnace guy as he's the son of a mover I worked with. HVAC companies probably won't have any idea. If anything, you're looking for Manufactured Home Service and Parts places. Call them and ask. No luck, call movers and ask them. They're usually well in tune with others in the business.
Doors, counters, carpets, floors, etc. often don't match. It's your call to put yourself in the buyer's shoes and think about what would make you buy or not. Detach yourself from the situation and think like the buyer.
This all goes back to value. I'll just put the ball in your court here and tell you what I tell ANYONE I've ever worked with/mentored/friend-ed regarding the business.
1. You have to know value. I have a real estate background and created massive spreadsheets with comparable sales, assessed value, market trend analysis, etc. to valuate a potential real estate property. As we all know that is not possible in mobile homes as there's no unified valuation system (for the most part). YOU'VE GOT TO DO THE WORK! This is not going to be fun, but I called every seller within 150 miles of me and created a spreadsheet with home details, location, and asking price. I asked them questions as if I were going to buy. I must have had about 60 to 80 at one point, and it was a full time job! Then I called back as time elapsed and asked if they sold. If they didn't, they were over priced. If they did, I politely asked with a loose script what they sold for. I got cussed a couple times but roughly 50% to 60% told me the sales price of what amount of cash they received. And then I had it, I had sales comps to be able to analyze the value and time it took to get that value. None of us know the values getting into this business and you have to start somewhere. If scared, use an option (I would each time anyway) so you minimize your risk. But don't go throwing them around all over. The manufactured home community is a word of mouth community. Of all the homes I've optioned, I've only had to back out of 2, and in both scenario's the seller's actually backed out and I was let off the hook. I tried VERY hard to close any option as that's your reputation on the line.
2. Read "Deals on Wheels" to understand the business in and out. Educate yourself.
I'll step down from my "pedestal" now and hope that helps your valuation of that property. Unfortunately there's no magic number that experience gives you; experience gives you the ability to set your own market values in your area. I now buy with my own properties purchased as comparable values for any new purchases. It works out very well as the values are always where I need them or I walk away.
Based on what their answer is if they don't sell, give them a 3 option offer. The highest price being 100% seller financed and maybe that's the $4000 that you said is their minimum. The second is $1500 down to help them get across country (ALWAYS ASK HOW MUCH THEY HAVE TO HAVE IN POCKET FOR THEIR NEXT STEP - USUALLY THEY'LL TELL YOU AND TIP THEIR HAND TO THEIR LOWEST SALES PRICE!) and the rest financing with a price of $3250 or so. Third is all cash at $2500 or $2700 or wherever you're comfortable. Closing in 3, 5, 10, or however many days you can "buy". Weight the option you want by making the other two un-desirable based on their scenario. I did this once and because it clouded the scenario of my offer and put the seller in the frame of mind that it was 3 options or nothing, and got the home for about $600 less than what he'd paid for it a week earlier. He explained that he couldn't wait on his money and so decided taking a loss was better than his other options...when previously had given no indication to his lowest acceptable offer - which I wrongly assumed was what he paid for it.