I've never been to the gym "United Fitness Centers" on Northern Blvd between 69th and 70th and have only seen it by driving by at night. There are usually people working out there when I pass at 10PM. Since it appears to only be a storefront I am guessing it is small but it also appears to be inexpensive. The website is below but it is a pretty lame web site since a lot of the links are broken.
http://www.unitedfitnesscenters.com/
I stopped by there a few weeks ago, but I can't seem to find the info card I was given.
It's not called United Fitness Center anymore, the name is something like NY Fitness (local resident should be able to confirm, I don't live in JH). I was there a month ago, so some of the details are sketchy now. It's a storefront-sized space, I'd estimate that it's 1500 to 2000 square feet (just a guess). The first 1/3rd is cardio, with bikes and treadmills. The middle 1/3rd of the room seems to be exercise machines (not Nautilus or Universal, but along those lines). Pulleys and plates and cams. The machines looked nice enough. The back 1/3rd of the gym is free weights, with dumbells (up to 100 pounds) a flat bench press, an incline bench press, a power lifting cage (nice feature to have), maybe a squat rack. I didn't see the dressing area but it didn't look large. The fellow (owner? Asian guy with muscles) seemed very nice, and no-nonsense. I can't remember the prices, but I'll guess that it was something like 199 or 249 for a whole year (cheap). I went during a busy time (8 pm?) and the gym was somewhat crowded, like every gym at that time, but definitely not unreasonable at all. I believe they are open until 11 pm or midnight during the week.
All in all, does not look fantastic, but if you live near 72nd and Northern Blvd. and don't want to drive to a gym or take the subway, then it's a good option. Going here makes a lot more sense than walking to Executive Fitness on Roosevelt Ave. It's smaller than Executive Fitness (EF has a whole separate aerobics room) but looks less crowded during peak hours, and not as beat-up and rusty like Executive Fitness.
Executive Fitness WAS a 24 hour gym Mon-Thurs (if the above poster is correct they changed their hours) which was a nice feature... if they changed it, too bad.