Shop lights. Four foot tubes are easily available, relatively cheap, and quite efficient. Use longer ones if you can get them and it is convenient in your situation, they will produce more light. Buy sufficient to cover the area of your seed trays. Buy cool white tubes, preferably the ones with long life without decreasing brightness which might cost a dollar more. You can also use "daylight" tubes (6500K temperature) or a mixture with warm white, don't use only warm white tubes. Plan your shelves so that you can adjust the height of the tubes or the height of the plants. Modern fluorescent tubes don't have to be almost touching the leaves but they should be fairly close. Plan on running them through a timer. Despite what you might read, most timers will operate fluorescent tubes, the mechanical ones with little push segments will work, electronic ones running a relay (they click when they switch on or off) will also work, a few will not work. Any timer which struggles to turn the lights on, causes flickering, bad humming, etc., will be damaging your lights and possibly the timer.

Wonderful. I think that's doable. When you say florescent tubes, are you talking about the same thing my DH has all over his garage? Or are they different? Also, would the "daylight tubes" be better or no matter?
Thank you for your advice.

I am pretty sure they are probably the same thing as your DH has hanging in the garage. 4 foot long fluorescent fixture, they have 2 tubes in each fixture. you can buy them at walmart, home depot, lowes etc. IMO its best to mix the tubes up and not have the same tubes in every fixture. daylight mixed in with cool white is good. stay away from the warm white. I'd also make sure the fixtures use the T-8 bulb which is smaller and more compact and the light is a little more intense. If possible hang them 6-12" above your seedlings for best results.

How many plants can I put under each light?..(Or) How much area does one light cover? I don't want to stretch the light to thin, but I don't want to buy more than I need this year. At the most(when it is time to thin and transplant) I will need lighting for 7 flats(18 full-sun plants per flat). They are about 1'x 2'. Do you think that if I put 2 flats end to end (area= 1'x 4') that one light would be sufficient for healthy plants?