If you're into solar like I am, you've no doubt run across those "Build Your Own Solar Panels for Free" (or cheap) schemes on the internet. Knowing a little about the subject. I looked into it and most of what you see is some cat on the side of the interstate in California, at a DOT solar sign charger, proclaiming in an accent "This is the solar panels I built for my vacation house for only $100".

No there's still no free lunch:

Buying the individual cells separately off places like eBay is easy and cheap. But you know nothing about the cell's output, if they're rejects, seconds, etc. Wiring them together is still fairly easy. But the real issue with any panel is longevity. Commercial panels currently last 25-40 years. Do you think you can cobble up some frame in your garage that will last that long, outside, through heat, cold, and storms? DIY is fine for a small 10-20 watt panel to use mobile. But a real system of any size (even 100w) is best bought. You can still aim to be economical. 

Here's the most economical panels I've found:
Kaneka GSA60 - 48v nominial, 60 watt - $1.40 / watt!

They are amorphous so the voltage output can be pretty high. For a small system, a MPPT controller like the BZ MPPT250HV would be perfect (250w) or the MPPT500HV (500w). Combined with (4) 12v deep cycle batteries in series and an inverter.

These together and you could have 250w up and running for about $4.82 / watt. That's cheaper than some panels just themselves. Solar systems typically run $8-10 / watt installed. Don't be fooled by sales pitches on the internet. Solar is still fairly expensive per watt but if you do your homework you can still make economical decisions.