The first trip I took other than mostly camping trips or nearby overnights with friends or specifically for just visiting family was when my parents were going to Florida to visit some extended family and then visit Disney World, Key West, and the Tampa Bay area. We got to talking and decided I'd join them. I met them there since we lived in different states, so I bought my own plane ticket. They paid for hotels (I shared their room) and rental car since they were getting those things anyway and in return I bought their 3 day WDW passes. We generally bought our own food, though I think they treated a few nicer meals at dinner time. That was my first "big" trip I paid money for - but it was with my parents!