As a Yungerman, I face the same predicament.
What worked for me was part-time teaching in a local frum school,
learning with baalei batim (make sure they know you expect payment upfront) and computer programming.
The biggest problem here is that all the above options require time investment where the salary is directly related to the time invested. This is obviously what Kollel guys are trying to avoid, but to find something that actually helps with the bills and does not require selling your time is almost impossible as can be seen from the suggestions given.
Many Yunderlite have this dream to start a business where they can work 3 or 4 hours a day and just watch the money roll in and carry on learning. To date I have not met a single person that managed to start such a business. Most of the people that tried this just landed up closing their startups and getting full time jobs.
Today I work as a programmer and learn as much as possible.