If you have harp insurance I’d double check to make sure your harp is covered when you rent it out, especially if someone else is coming and picking it up. When I applied for harp insurnace I had to state who was transporting the harp, whether it would ever be out overnight, and many other specifics on how I’d be moving and storing it. Besides that, you should think of making sure you know the conditions where it will be played and kept when not in use and a general agreement of what to do in the event of damage. You might also see if there are some sample clauses on the internet or in some self-help books in a library for provisions where she agrees to be responsible if your harp falls on a child who probably had it coming by trying to climb the column and think about whether you want reimbursement for broken strings, and I could probably go on. Not that you’d need to include every possible event in the contract, but you should at least think about what you’re willing to risk or pay for and what’s worth spelling out. You probably saw the other thread here about someone who had terrible luck renting their instrument out. And get paid ahead of time with a good check.