The least expensive way to start seedlings indoors is to use a standard 4-foot fluorescent shop light. Special grow-light full spectrum tubes are not needed. Instead, use a mixture of regular cool-white and warm-white fluorescent tubes.
Because the tubes need to be very close to the seedlings, the shop light fixture must be adjustable up and down. This is easy---all you need to do is suspend the fixture by pieces of light chain. This allows the fixture to be moved up or down one chain-link at a time.
Assemble the shop light, if necessary, and install the fluorescent tubes. Make sure the tubes are securely locked in place in both ends of the fixture's slots.
Measure the distance between the hanging holes on the top of the fixture. Install the screw hooks (in the ceiling or an overhead beam) the same distance apart.
A basement is the easiest place to use for your plant light installation, because the overhead wood joists are visible. If you are working in a room with a finished ceiling, you will have to locate a ceiling joist to hold the screw hooks. Plaster board or Sheetrock® are not strong enough.
Hook the ends of the chains to the screw hooks. Attach the other end of each chain to the shop light fixture, making sure this connection is secure. Now raise the fixture about 12 inches off the ground by adjusting the chain where it attaches to the screw hooks.
Set the timer so the shop light will remain on for 14 to 16 hours a day.
Connect the fixture's power cord to the timer, then plug this in to a grounded electrical outlet. Ideally this will be a GFI (Ground Fault Interrupter) outlet, because seedlings need water, and electricity and water is a dangerous combination! A GFI outlet greatly increases your safety level.
Place two standard size (21- by 10½-inch) seed trays under the lights. Adjust the chains so the fluorescent tubes are about 4 inches above the seedlings. As the seedlings grow, keep raising the fixture to maintain that distance. Do not allow the seedlings' leaves to touch the tubes.
Every couple of days, turn the trays 180 degrees so all the seedlings get equal time under the cool-white and warm-white tubes.