You could utilized sharepoint lists and build an app to do what you want.
SP Lists
Items -> ID (Auto SP), ItemName, CheckOutOn, CheckedOutBy, ReturnDate, etc...
Users -> ID (Auto SP), FullName, Email, Phone, MaxItems, Rating, etc...
Ledger -> ID(Auto SP), FullName, UserID, ItemName, ItemID, Status, etc...
Items is where you store all the info for the items. This would be essentially an inventory of what you have to loan out and would track when something is out, when it should be retured, and who has it checked out.
Users is where the users that rent something are stored. A user could simply sign in using thier tenant UN and PW and then use their full name and email from that or you could just have the users make a unique login UN or use thier SPID assigned to them when they create an account. This list will keep a record of all users that have used the app and can also be used to keep a rating for each user. If they return the item on time then give them +1 status/rating and if they dont then they lose 2/3 etc.
Ledger is the list that will track each individual 'rental' of equipment. If John checks out an IPad and a Charger this is the list that will be stored in. This will be a running history of who has checked out what equipment when and for how long. This will be useful to see the chain of renals/ownership in case something gets lost/stolen etc.
When the app loads if the system cant find an entry in the Users List for the entered username then the user will be asked to make a profile really quickly. Once that is done then take them to a screen where they can choose the equipment they need and check it out. This could send them an automated email receipt with the check out/in times as well as any legal jargon you need them to have.
You could always add the items SharePoint ID to a sticker/label on the devices then when the user returns the item they can just type the ID and it will find and return the item and mark the ledger item as returned etc.
Hopefully this helps you get started! 🙂
