There are many multi-process units available , Miller even has a mig/stick/tig unit now and it's priced around 1800 new , won't find a used one for awhile . Older used transformer migs are affordable as long as they are in decent shape and not abused . Duty cycle is most important - if it's been ran a lot up against or over it's cycle they can degrade a lot and will never weld very well . Keep your eyes open , deals do come up now and then in sale papers , ect . Decent welders on Craigslist and such disappear very quickly . Don't discount a stick welder - I've welded body panels in with 1/16" 7014 rod using a stitch method , not easy but it can work . Anything thinner than 20-22ga sheet is pretty tough to work with , even with a mig if you aren't experienced . Cruiser body parts are easy , I'd just use a stick on them here over the tig - it's faster anyway doing stitch and no gas cost . Any stick machine that is dc can be used for tig , just have to use scratch start and whip out of the puddle to finish or make a breaker switch . Keep in mind most stick machines are ac , at least the cheaper ones . AC/DC units aren't cheap and harder to find .
For a lot of stuff , a good used Lincoln 140 or the Miller version is great for beginners and do hold their value quite well - always someone wanting to get started and they are always out there from someone working up to more power . Just make sure it's in good shape and not beat up , take a buddy that welds a lot for some testing and push it a bit hard and see if it overheats easily .
Best advice , spend some serious time on the weldingtipsandtricks.com site - Jody is an ex-instructor and experienced in the aircraft industry , guy is excellent at explaining things better than I ever could . Never , ever skimp on a hood , especially those junk-ass Harbor Freight units . If nothing else , buy a used auto-dark or just spend the $30 on a new Jackson #10 and learn to tip it - there are videos about how to prop yourself so you don't get lost and weld something not intended or cause damage . I cannot express how important it is to protect your eyes , trust me on this please - it doesn't take a lot of time to do a major amount of eye damage . Good hoods have great clarity and it does make a difference - borrow someone's good Jackson or whatever with a "gold" lense - they are amazing .
Honestly , I'm not that good anymore , going slowly blind due to severe myopia - most of the time my helmet is clear down to 8 so I can see , even at 150a on the tig . Not nearly as steady either , I hate arthritis . Used to be able to weld anything - broken heart and the break of dawn....now I can't find it to get started , lol .
Sarge