Randy,
Really depends on how much fence/deck you have. I own a Campbell Hausfeld airless sprayer, see the link, but I spray a lot of barns and fence.
I've owned it for ten years with no worries at all. The C/H folks have a wide range of sprayers, one may fit your needs.
More is better when it comes to these things, btw. Don't be shy.
All the best.
Morgan
http://www.jackssmallengines.com/ch_paintsprayer.cfm