Proper Mountain Biking Safety

Can I fit disc brakes on my mountain bike wich was not designed fro them?
Ì have a pretty cheap mtb, I want to accumulate parts to eventually build a good bike. I would love the control and safety that discs offer. The frame i have does not fave mounts for a calliper per say, however it has 2 bolt holes which i think would normally be used for a carrier or maybe a mud gaurd. They’re pretty standard on bottom end bikes. 2 holes located above the rear dropouts on each side of the bike. Can i get adaptors or something to bolt into these and then provide the proper spacing for a disc brake calliper? Surely somebody has designed a solution to this problem?
They make adapters for non-disc frames:
http://2btherapy.com/index.php/bikes/brake-therapy-conversion-kit
But you’d might have more money in them and the brakes than your bike is worth.
I’d recommend getting a low-end bike with mechanical discs as standard equipment. You can nab one for around $600.
Mountain Biking Safety : How to Jump Off a Mountain Bike

