Welcome!

Depending on where the Excursion is from, check everywhere for rust, especially rocker panels. Broken manifold studs are common, but if you are moderately mechanically inclined you can replace these over a weekend of cussing. The steering on these gets sloppy(tie rod ends and ball joints. Obviously records of general maintenance would be good. That is a really low price, if all the common issues are there and it still runs well, id jump on that. On the other hand, id be asking a lot of questions and doing a thorough inspection so as not to buy a 2000 dollar lawn ornament.

Hope everything works out, pictures are mandatory for the forum if you purchase

 

 

You are in NH, so I would expect it to have some rust, especially at that price. As mentioned the exhaust studs are a common issue with these motors, give them a good look. They are a pain to replace but can be done in the driveway, I did mine.
Pay very close attention to the trans, run it through it paces and make sure there are no strange noises or odd behavior, a new trans will cost more than the asking price of the EX. Be sure to check the trans fluid level and color.
Operate every option to check for proper function, again, for the asking price I would expect some to be non-functional.
Take a code reader with you and check for any codes and or pending codes and make sure the Check Engine Light lights when the key is turned to the ON position.
Give all of the frontend components the old wiggle test and check for steering play when rolling on a flat straight (is there a flat straight road in NH?) roadway.
Ask the seller to have the engine COLD when you come to see it, then you can check for any smoke on cold startup and listen for any odd noises before it warms up. If there are missing exhaust manifold studs expect some tapping exhaust leaks when cold, they should take up for the most part once hot. Inquire about the most recent spark plug change and any other maintenance.
Good luck, I hope you find a diamond in the rough.