I made a grow light from 2 small 150W HPS security lights. We used to be able to buy 150W security lights for about $20 (I got mine at a storage unit sale for $2 each), but they are not available anymore. They worked quite well. There is a link in my sig. You are going to have to have some building skill and be familiar with simple electrical if you are wanting to build something yourself. Unfortunately simple and inexpensive usually do not belong in the same sentence...
You will need at least a 400W HPS for that space--larger if you are going to use MH rather than HPS as the MH put out fewer lumens per watt than HPS. Lighting needs are figured by lumens per sq ft--you want a min of 3000 for vegging and 5000 for flowering. You also want different light spectrums for veg and flowering. MH is okay for vegging, but HPS is better