This is a link to the a starter sized loft. I see this one recommended quite often by Pigeon fanciers.
http://www.redroselofts.com/starter_loft.htm

I consider this loft a bit overboard for someone wanting to keep a few birds around for training dogs. But it is quite nice for someone looking to race pigeons or keep pigeons as a hobby it is a very nice loft.
Here is one of the best ideas I have heard for a low priced loft to keep a few bird in. Check with shipping companies to see if they have any large wood crates. You can often find them very cheap. Similar to these.

Obviously they come is various shapes and sizes. Lots of possibilities to customize a small loft. Last time I called a place they had several for $35.00. I didn’t end up going that route, but costwise I should have.
If you are not feeling too creative Lion Country Supply has some plans for a small loft which you can buy for $5.95 Loft Plans



