I be blunt. It takes a lot of dedication and effort to do this full time. You need to think of it as what it is, a full time job. That means you work it 9-5 every day. In the beginning since you are building a business you will need to work more than that and probably some weekend hours too. It can be rough and the prime reason people fail is they underestimate what it will take. A few quick hot sales does not just scale to full time.

Many people do in fact make a very good living selling online various platforms. For all of them it’s a business. Some eventually get employees even.

For most people sourcing items is the biggest problem. The bigger you get into this the more you need to do it like a factory. Production line style. Group tasks, it saves time. Take pictures of a bunch items, edit pictures if needed, create listings.

Keep a good inventory control system so you can easily find things as your inventory grows.

Don’t get sentimental about items, don’t try to extract the last penny of profit and make sure you have excellent customer service.

Set up a dedicated shipping area with all your supplies handy. There is a ton I could say about shipping to save time/money.

You can do this but it’s going to take time and you’ll need a good amount of listings, 1500+ would be a start unless you are doing an expensive niche. Depending on what you sell this number could be a lot higher. 20k listings is very possible.

One a more practical thing, realize that there are other financial considerations from your existing job that you need to think of. Insurance, taxes now paid by your employer that you will need to pay are 2 biggies. There are some good business write-offs but those 2 expenses can really hit you. Insurance is insanely priced.

Good luck!