My seed starting area is nothing more than shelves in my greenhouse (cold frame) with the following items...
Seed starting trays $5.00 each at Wal-Mart
2 Flourescent lights fixtures cheap $9.00 model
4 white flourescent bulbs (can't remember what I paid)
2 Heat Mats not so cheap around $25.00 each. I bought them last year. You can use an old heating pad.
4 Coleman Emergency Blankets about $2.00 each
I used two coleman emergency blankets draped over the top, back and sides of the shelves. I use the other two draped over the front to retain the heat and to keep the glow of the greenhouse from bothering the neighbors at night.
It stays nice and toasty at about 65 to 69 degrees when it's all closed up with the heating mats on and the lights left on until 11:00 P.M. Even with the night time temps in the low 40's mid 30's. We only get a week or two of frost in Jan and Feb.