Hey y'all. You all have been so helpful. Thank you so much.

This will be a bit if a shotgun post here. Please tell me if I should delete this and make a separate post for each problem found to keep things organized.

Got my eye on a 77 era coach that's local here and did my first test drive on it. Found the following possible problems that I'd like your opinions on.

Dash heat. We ran the coach for over an hour and the heater never blew warm. It was 45 degrees outside. Owner didn't think it was broke just "inefficient". Something about the long distance the water had to travel around (to the house water heater and back he said). Total bs or is that normal for these coaches. (Sure hope not. Wife will definitely murder me if we can't have cabin heat) What things could cause that and how much to fix? Ballpark.
=> The heat should work. It is more effective than you have experienced. It could be a 20$ valve or it could be something else. Another reasonable be is that the control needs work. This can be anywhere from a few dollars for a new pin up. The fan worked? That is a good sign.

Exhaust fumes. When we drove around the coach smelled of gas and fumes. He explained it away as the tank being "too full". True or bs. What could cause this? How much to fix. Ballpark. This is also a non starter for the wife. She gets migraines pretty easy if she's trapped in a room that has bad chemical smells. Pretty sure carbon monoxide would make that list of triggers.
=> There is no reason at all for this. There are exhaust leaks somewhere and if you could not hear them, I would not know where to start.

Some Road drift and loose steering - I think. The rig has just shy of 120k. Suspension never rebuilt. He's Running Alcoas and firestones. Owner said it drifted a lot more when he had Michelins and he feels it rides fine. Im sure I do need to drive more GMCs to see if it's just me or if they all drive like this. Assuming I need a rebuilt front end - what would this cost. Ballpark of course.
=> Either the steer box is mis-set (an incredibly common issue) or some parts are worn and loose. Nothing is all that expensive, but the work is involved.

he didn't demonstrate the dash or roof ac - said it was "too cold" to show the AC works but he said they both worked.
=> This is possible as most A/C will not function at all at low temperatures.

he didn't have the refrigerator lit off. What's a worst case scenario (parts and labor) on a replacement refrigerator in case it turns out to be beyond repair.
=> See if it works on AC. If it does, the gas part can be fixed. Worst case is about 300$ for a board and a burner. Burners can usually be cleaned and then they are good for a while. If it is really dead, a rebuild cooling unit is a big hole in a kilobuck, but a replacement is ~1.5. Or you can get an inverter and a dorm reefer to put in there. (mine was <200$ but very battery dependent)

It's never been converted for ethanol tainted gas. Conversion estimate?
=> All the rubber has to be replaced in the fuel system. This includes the selector valve and engine pump. The tanks have to come down. This is all something you can do in a hard weekend and cash out of pocket is less than 100$.

He keeps the airbags in "auto" and not "lock" contrary to the instructions stated on the advisory plate. Is this bad. I seemed a tad suspicious especially since I found a post he did on here asking about a problem with the level system several years ago. He says it is working to spec. I don't know enough about it to know if his demo Of it showed it worked after all. It seemed to slowly go up and down as he hit the controls while I watched outside.
=> If he has the switches in "Auto" (Mine says "Travel" but it is older) and it is holding ride height, there can't be anything wrong that amounts to anything.

Last, the seats wouldn't slide forward. What do new or restored seats cost if it can't be repaired or just operator error.
=> Most likely the later. Even if they were seized up, the can be cleaned and greased.

Trying to get a rough idea of what I'd be into $$ wise - worst case scenario - if all these things require repair/replacement (assuming I had it all done for me at a shop).

I understand this is asking a lot not knowing what actually is wrong in each case. Just trying to Get a sense.

Other than these things I liked the coach based on my shallow knowledge of these so far and with nothing to compare it to.

He was an otherwise really nice, older gentleman who said he was selling it because they are headed to the "old folks storage facility". his words. To be fair he knew a lot about the coach and could be spot on with all of his assessments. He seems motivated to sell and I may make an offer (it has a rear bath and was maintained by Ken Frey and has all records since new and a new galvanized frame which like) especially if he concedes these costs and adjusts the price accordingly. (He listed the price based on "everything works" and was surprised I brought up these issues) so I think an adjustment would be fair if they turn out to be real issues. Naturally I'll pay to have a shop draw up estimates to get a more exact idea of what to offer him if we get that far. Mostly just want to know if you all think this coach would be worth the time and expense to take this next step or is this sounding like a lemon and I should just move on.

Thank you in advance.

Jason

Our dash heat decided to quit working on a cold, rainy trip between Las Vegas and Parker, AZ a few weeks ago. I have diagnosed it to either a bad heater control valve or a plugged heater core. It should blow nice and hot, warm anyway.

The gas/exhaust smell could be due to a leaky hatch cover gasket and/or exhaust leaks as Matt suggested. These are easily remedied.

Have not read in this thread about fumes possibly coming in due to chipmunk cheeks (the separation of the front cap and floor at the front wheels), the body will have a bulge out at the front wheel area.

Just something to check.