The prevailing wisdom on HN is going to say networking and word of mouth.
If you don't have an existing network freelancing/consulting is going to be very difficult. I've tried the online freelance website method before while I was in college. It sucks. The clients don't want to pay even a reasonable amount and they're usually pretty shitty clients to work for.
If you have a network I'd suggest consulting. If you don't then I'd say steer clear.
Though I guess the beauty of it being something on the side when you have a job is you can advertise your services and not worry if nothing come through.
An honest question, what would it take for you to pass on leads and/or generate leads for others? I'm thinking of a blockchain based venture to support payments for finder's fees. Thanks.