These were my first thoughts as well.

I rent time on a long arm. I had to take a class to learn how to use it--I forgot almost everything by the time I had a quilt ready to quilt. The class cost was $100.00 plus a set of zippers to use to load the quilt. The charge is $20.00 an hour and I use pentagrams. I'm not nearly good enough to even meander yet. It usually takes 3-4 hours, and I love it. The owner is right there to help the whole time, I have to sign a contract each time, and they supply one needle. If I break the needle, I have to buy more. Don't know how much that costs. The cost is about the same as having someone else do the quilting, and now I can say I did it myself. If I owned a machine, I wouldn't rent it--the repairs are hard to get and your machine is out of commission while you wait for repairs.
Sue

IMO your first step is to talk with your home owners insurance agent. You need to determine how much liability is on you. Also, you need to make sure that the cost of your machine is also covered by your insurance. Most policies have a cap on the cost for replacing items. I have an additional rider on my policy to cover my machines.
When I was in the plans for opening a store, this is an issue I had to research because I was considering renting longarm and domestic machines at my business. Now my research is for the state of Missouri so you will want to research for your state. Also, some of my information is from an attorney.

Per the attorney; If a rentee does damage your machine don't even think you can get the rentee to pay for the repairs. That comes down to way too much they said/I said and most judges will rule in favor of the rentee because it is "implied" the owner is willing to cover the damages.
Per the insurance agent; If the rentee becomes injured while renting the machine, the owner is liable for any and all medical expenses incurred by that injury. I know you say it is your friends wanting to rent the machine BUT when it comes to an injury, experience is speaking here, friendship will quickly come to an end. Injuries can be: needle breaking and flying into an eye (yep this does happen), sewing thru a finger (done this twice myself), falling while running the machine (tripping over one's feet comes to mind), getting an electric shock from the machine (I've not had this happen but have heard of it happening), and this list can be forever endless. As my agent said to me, "Even if you think something will never happen is just the time it WILL happen." There are certain things you can do for protection of others but you really can't cover them all.

Then in addition to all of this, you can still have several problems; you have a quilt you need to get done as a gift and someone else is using the machine, someone is working on a quilt and you have an emergency come up, and once again this list can become endless.

IMO, if you really want to keep the friendships, DON'T RENT YOUR MACHINE. That is just a disaster looking for a place to happen.

If I would ever be lucky enough to be able to afford to buy such a wonderful machine, I wouldn't let anyone even touch it!!

One of my LGS makes you first take a lesson if you've never used a LA - cost $50. Then once you've learned how to use one it's $20 an hour. I would sit down with them and be very honest in telling them what you would expect from them (liability if they break something, how much help they could expect from you, cost of supplies - thread, needles, etc. Get the tough questions and answers out of the way BEFORE they come up.

I rented a LA with a friend at the LQS, we were only doing small quilts. They charged for a short class on how to load and how to thread the machine. It takes time to load. We were very careful. If I had a LAQ I would nt let anyone use it. They are expensive and what happens if it breaks?

Thanks to everyone for your thoughtful advice. There is alot to think about.

i've been doing this for years- i start people out with a (certification class) where they learn the machine- threading, oiling, cleaning, winding bobbins---checking tension---all that- then we load up a practice quilt for them to quilt- the class takes 4 hours (usually) and when they are done they can then rent time for $20 an hour to come in and quilt their own quilts- i do not stand over them while they do this= i help them load and make sure they get going ok-then i usually go to my sewing room to sew- i am available if they have a problem (seldom happens) most of the people who have come in and done this have taken the class- come back and quilted one or two quilts then they seem to decide they would rather pay me to quilt their quilts instead and they go back to just dropping off quilts.. it is always fun to give someone the opportunity to try-

There is a place near me that rents their's for $40 for 5 hours. They teach you how to use it before you start. It is really nice for me since my hand sewing skills are not good. It would take me forever to hand quilt one.