Having wanted braces to fix my bad cross bite for most of my adult life and also hoping fixing my teeth would help my TMJ problems , I decided to see a local dentist who does free Invisalign consultations to find out if Invisalign was right for me. He said sure, 18 months max. Before I could even see the video of what my teeth could look like, I had to pay 1/3 of the overall fee (around $3500). So I paid that, told the dentist about my TMJ problems, had the impressions done (which was an ordeal in itself since they didn't have a tray that fit my goofy upper teeth) and hoped for the best. When my trays came in I had to pay off the rest of my bill, so by three weeks in I had already spent $3500.
Then the problems started. My upper and lower molars were just too close together so that when I had the trays in my mouth, they forced my jaw apart unnaturally, causing a major TMJ flare up that only went away after I had the trays out for a couple days. Realizing that Invisalign was NOT for me, I went back to the dentist and was refunded $1000, but the guy kept $2500 of my total fee. I don't even know how many trays were in my initial kit, but he told me my fee included not just the first Invisalign trays, but future revision trays (that he told me I would need) as well as fees for each office visit every two or so weeks when he would give me another tray. In other words, he not only prescribed Invisalign to someone for whom it was not suited, he also ripped me off.
Instead of doing the 18 months on Invisalign, I went to a highly rated orthodontist and am now in my 8th month of ceramic braces and almost ready for retainers. Plus my TMJ hasn't flared up once with actual braces. The orthodontist also offers Invisalign and told me point blank it was the wrong tool to do the job in my case and he wouldn't recommend it for my teeth. My advice is to get a consult with an orthodontist that also does Invisalign before going with a dentist. You may find that braces are not only the better option for you, but are quicker, too.