Buy and sell business

I am looking into the buy and sell business side, I know how to sell that’s one thing I do very well… I just need some good ideas of what to sell. My plan is to find a manufacturer or a supplier for the “product” and sell that product online. I am making it sound like it’s easy I know it’s not I just have a very busy life atm and I would like to start making more money on the side so if I could literally just get the product in, and advertise it and post it online and make some extra money on the side it’d be great. Any ideas on what products to sell ? I am based in UK