I've been giving out loaners for years now. As an in-home tech, who also works a "day job", leaving a loaner gives me much more time to work on a system without it being an inconvenience for my customers. It also helps enormously when I'm trying to earn trust from a new client who is not a referral. If I'm leaving them a computer of my own, they feel like I'm not planning on stealing their computer that I'm picking up. Additionally, having them back "up and running" right away is a major plus.
I have 3 desktops, and 2 laptops. I update / image the machines every other month (I use D7II auto-mode for this). A few tips if your looking to start doing this:
1) use Snappy Drive on-site to install their drivers on-site. I have the default driver packs downloaded to my flash drive, which helps to eliminate/reduce download times.
2) I have installed Prey (preyproject.com) which allows me to remotely disable the machine in the event of theft. I've never had to use this, but it's there if I need too.
3) All the machines are cheap/disposable. The laptop's were $300 black Friday specials, and the desktops were under $300 builds. If someone does steal one, I feel like I've already gotten more than their value just in having the service available (3 or 4 jobs and their paid for)
4) I always ask if there was any sensitive data stored on the machine on pick-up. If there was, I DBAN the system prior to restoring the image (never know if the next 'customer' might run data-recovery on the drive)
5) Password-protect BIOS to stop them from booting to disk & re-loading Windows
6) If you really want to go all-out, use XOSL to have multiple OS's on the machine. My desktops have Win 7, Win 10, & Win XP. This is great for my "challenged" and elderly clients that can't handle a different OS than what they are used to.
7) Have a remote-support client loaded in case they need help doing something simple, or you need to send them a file from their system.
8) Either run your own WSUS server, or use WSUS Offline to install Windows Updates. I use PatchMyPC to update all the 3rd party apps
9) I used a case with a handle on the top for the desktop builds. Look's very professional & is much easier to carry into a house.
10) For the desktops, use a MOBO that has VGA, HDMI, and DVI outputs.
11) Try to make the system run as quick as possible by upgrading the RAM and using a decent HDD. Many a customer has had me do custom build for them just because my $300 loaner runs better than their main system does.