m-dot Ironman races cost $550-600, but non m-dot races are more like $300. Many of the m-dot (official "Ironman") races sell out way in advance, within days to weeks of going on sale, but the non-"Ironman" Iron-distance races don't have quite that problem.

I train for 6 months (24 weeks), I think the training time for both is actually pretty similar but the Ironman obviously ramps up a lot farther. The first 3 months are base building and basically are 4 days a week at ~2 hours (2 days run or ride and swim, 2 days run or ride and strength), weekend days at 2-3 hours each ride plus 1 swim, then it grows from there to a peak of 4-5 hours ride and 20 miles run on the weekend at peak plus one day swim (and the 4 days a week at 1-2 hours).

It's great for the first 4 months. Month 5 is hard - the most hours dedicated to training. Month 6 is brutal mentally - you aren't there yet, you're tired of it, but you have to keep going. It helps to map out where that would fall with your target race so you know what to expect with work, family, and other schedules.

Doing a Half Iron first would be a good experience for knowing if you want to do the full distance, but if you want to go all the way there's no reason you can't - that's what I did.