Many dealers have spring "shows", usually in March, and that is a good time to buy equipment if you want really new, 2004 mowers. Right now may be a good time to look at equipment because some dealers probably want to get rid of some of their 2003 equipment.
I would go with a wood plank floored trailer. It is easier to repair. Also, if you want to modify the trailer the wood floor gives you an easy place to drill or attach stuff.
If you are working alone, you only need one piece of each equipment. The problem is breakdowns. If possible, try to get "backups" for your main equipment, even if it is old. It doesn't have to work great, just until you get your "main" equipment fixed.