Yes, you could be a RE agent as a side hustle working primarily nights and weekends. Would you be very successful? Probably not.
The average income for a RE agent in their first five years is around $20,000, i.e. about minimum wage if you were working full-time. While a lot of activity happens on the weekends and after normal working hours, you would still need to be able to answer the phone and respond to emails during the day. Depending on your full-time job that may or may not be possible.
Think about it from the point of view of your potential customer. Will this person who is a part-time agent be able to sell my house quickly and for top dollar, or am I better off going with an agent who does this full-time and potentially has years of experience and a network of potential buyers? You're both probably going to be charging the same standard 6% commission so unless you're willing to drop your price, what incentive is there for a seller to choose you? The only benefit you have is either you are cheaper or you can promise better service because you may only have 1-2 listings versus that other agent with 10+. On the buyer side, same issue.
RE Agents have a low barrier to entry and the field is crowded. The Pareto Principle (aka 80/20 rule) is very pronounced. In some cases it may be more like a 90/10 because so many agents are part-time.
One thing you could do as a side hustle is bird dog deals for investors. You find a property that would make a good investment, either as a rehab, a flip, or a plain old rental, and you get it under contract at a good price. Then you assigned the contract to an investor who pays you a finder's fee of $1,000 - $2,000 (or whatever you negotiate) because you found them a deal that they can make $10,000- $20,000 on. This is something that you can do during evenings and weekends. You can walk through a neighborhood and find houses that look like they're vacant and maybe don't show up on anyone's radar as being in foreclosure or pre-foreclosure. Talk to the neighbors or look up public records to try and find the owner and make an offer.