There are cheap pH testers (available from most garden centers & mail order houses), and they also offer a version that also reads
NPK.
The pH testers are "relatively" accurate...they'll tell you if it is alkaline/neutral/acidic...but don't believe the actual numbers they give you. I have heard too many people tell me that their numbers were
way off from what lab reports said. They can still be useful as a way of seeing if things are swinging one way or the other, but not accurate
enough for planting purposes for plants that are picky about their environment.
From what I have seen and heard, the
NPK info they provide is so far off that they are essentially useless.
Contact your
local Extension Office, as they often provide free/cheap soil testing through their university. These tests generally cost less than one of those crappy meters. Plus, they will provide you with info on how best to take your samples.