I am the same, never been but always wanted to - and so have now got it in the planning for next year! I know its not going to a cheap one but for me it will be a once in a lifetime trip. Your welcome to tag on if you want - and can wait until next year!
If you can find homestay accommodation that helps with the cost or camping, but the ferry prices increase for TT and be aware that the cheapest petrol here is £1.179 a litre at the moment. Also cost of living on the Island is more expensive than the UK, but its a good crack especially if you have the time to do the latter half of practice week and all of race week.
We regularly go the IOM a week before the TT, the ferry, camping (or B&B)fuel, food is all cheaper when the TT isn't on but the best bit is the track is set up, signed & painted so you get to do 100s of laps with dealing with floods of bikes & cars or the police closing the mountain every two mins.you also get to walk round the paddock as it is all quite people are more inclined to chat with you. Sure you miss the actual races and the atmosphere but I can definitely recommend an early visit. I'll be there this year on our bikes