I figured I would share some real numbers so that you can get an idea of what kind of money you could make reselling things. I've only gotten back into selling things in the past month or so. I've really only been selling things to clear out space and clutter in my house and some things for my parents as they are downsizing.

I sold 5 Items on eBay, 3 within a few hours of each other! One had been listed for over a year and sold after I adjusted the price down by a few dollars. After fees, ebay paid me $196 and I spent $48.14 on shipping (this included a sixth Item that sold late last Saturday night.)
I also sold two Items on FB marketplace for a total of $90. $237.86 total for the week isn't too bad. I currently have a total of 38 Items listed on ebay 21 listed on FB and some listed on Nextdoor and I want to crosspost to CL if I have time, but the traffic just isn't there.

I've been breaking my own rules about Item value and listing things in the $10 range on ebay in the hopes that I can get my account back up to Top Rated by selling at least 100 items within 1 year. This will give me more protection against scammy buyers.

I also fought off 2 negative feedbacks this week! One had an item break in shipping, and they immediately gave negative feedback before contacting me to get a refund. The second person bought the wrong item, It was a new in package refill for something and they have a different model. I was able to get the first buyer to give me positive feedback after they got a refund and the second one changed theirs to neutral, which is better than negative. I believe eBay has changed the prompt to buyers asking them how their experience was, which makes people leave negative feedback without realizing they are grading the seller.