As said above T5's are great for vegging. I use a 6 tube 4ft fixture with another single 4ft as side lighting in a home made 3ftx5ftx6ft closet Bathroom fans for intake and exhaust. After my initial purchase I needed replacement bulbs and I found them as expensive to buy 6 new tubes as a new fixture with tubes included.....until I found 5 HO T5's from
Vivosun for $30 Cdn....A cheap brand I've had issues with some of their stuff but I took a chance because they are cheap and they work fine...good light and the plants are responding to them very well. I also had to replace my 2 tube 2ft t5 tubes for my clone/seedling box. I could only find Sunblaster t5 HO tubes at $20 each....
You won't get much flower from T5 lights though. If you don't upgrade to something made for flowering you'll be sadly disappointed after months of vegging then months of flowering to end up with fluff homegrown 70's weed.