Closed loop systems can become very dangerous very quickly if you don't have a thorough understanding of the process. Even once you know a good deal about the basics of vapor pressure etc.. you can have potentially dangerous situations from a wide range of things that are not immediately intuitive, things like;

• leaks due to drastic temperature change on o-rings.
• leaks in when pulling vacuum despite a successful positive pressure check.
• Air getting into the system while can tapping.
• Locking vapor into an area and allowing pressure to build through temperature change.
• debris in gaskets causing leaks etc.. and this is all assuming that your equipment is in perfect working condition..

If you're looking to buy cheap equipment, on top of all this you're also going to have problems like quick connects that fail, bad recovery pumps that leak oil into your system or fail due to not being designed for extractions, welds that leak, sight glasses that crack.. the list goes on. In my opinion you've got to be willing to spend the money on good, safe equipment or not do it at all.

THAT BEING SAID! When I started a few years ago I could barely assemble the machine myself (mkiii) despite being a mech eng. Not confidently that is.. What I did was I booked a flight to Fort collins,CO and received training at the Terpp location. I also spent ridiculous amounts of time online reading every shred of information I could find, in particular things by skunkfarm and Greywolf.

I would suggest doing the same, mkiii by terpp, but only if you are willing to spend the time assembling it yourself, learning every bit about it meticulously, and not skimping on cheap parts. Then start with small extractions outside in an area where butane can't pool and if you do have catastrophic failure you aren't risking anyone else. . If you're interested I will make a very detailed "how to" on my methods of using the Mkiii.