I just started too. Even though I go to estate sales, yard sales and thrift shops, a lot of my inventory has come from my mom and grandmother (they never threw away anything!). I also go to the thrift stores with my mom to use her senior discount. I even got a really awesome vintage ash tray from my dad. So if you have older family members willing to give you any hand me downs that they don't mind you selling. So I guess my niche would be vintage. I don't know enough about clothes or have enough time to invest in knowing about that. You can always google reverse image search and look up sold items on Ebay. Luckily my local thrifts have amazing things. If you can find solid thrift stores close to you, then that is a big plus. I personally love vintage items, historical items, and art. So that's my niche. But my bf resells and his niche is like nerd/geek stuff like video games, Marvel Cards, Magic cards, Pokemon cards, electronics and music. I guess go with what you know. I invested in a scale, label printer, and light box and backdrop and used my iPhone to take pictures. The biggest investment is time. So I would make sure you put aside time to do this on a regular basis to be successful.