Since you remain responsible for rent if the sublet doesn't pay, you are SL's landlord.
Go read the residential landlord tenant act for how to evict him. See if you can buy an eviction kit from the local process servers/legal services company. It will contain all the forms you need, instructions on filling them out, and instructions on how to proceed in an eviction. BE VERY CAREFUL that you give proper notices and serve the SL correctly. The landlord tenant assn. can also help you.
Should cost about $30-$90 to evict SL. You get a judgment for the back rent you paid + late fees you paid + attorney fees + costs (the $30-$90) + the costs of finding a new SL + the rent on the place until you find a new SL. This could easily total $2000. It should take about 2-3 weeks from start to finish.
To collect the judgment, buy the garnishment kit and follow its instructions. Garnishment is much simpler than eviction.
Alternatively, you can hand the case over to a collection agency, which will take 25% of everything they collect and give you the rest.
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This is not legal advice and you are not my client. Double check everything with your own attorney and your state's laws.