I currently rent a small office space for $250/mo. When I moved in, the place was a dump. I completely remodeled the space and it is a really nice office space now. However, I just moved 45 minutes away, and the commute to work is killing me. I plan on moving back to a home office, but I want to propose to my landlord to let me sub-lease the space, so I can try to make back some of the money I put into the office. I believe I could rent the space for $500/mo.

I don't currently have any sort of lease, I just rent on a hand-shake agreement. If I sublease, I would obviously propose creating a lease agreement and sublease agreement. 

Before I propose this to my landlord, do you have any advice on any terms I should suggest, or any other things I'm not thinking of?