My thoughts on avoiding "sinking a ton of money into repair and replacement parts:"
- Identify a few bike models that would be ideal for you before you go shopping. This way you wont have to change this and that component to better suit you.
- Know your ideal size. Buying the right size for you means no swapping of stem and seatpost.
- Find a garage queen. This is not so difficult if you are patient. Bikes are one of things people tend to buy but not actually use. You may have to re-pack some bearings regardless, but grease is cheaper than chains, freewheels and chainrings.
Enjoy the hunt! Come back and post some pics of your bike when you find it.