Whether you’re renting your first apartment or your 37th, chances are your eyes glaze over when someone hands you a 15-page lease to sign. What could be worth contesting? Would you even be able to contest an illegal clause if you found it?

All of us — but especially New Yorkers — assume that there are hundreds of other people waiting to take our dream apartment, so we better act fast.

According to some research from Harvard Law School, we have been signing leases on apartments and houses for decades that contain illegal or unenforceable terms. The study analyzed 70 lease agreements from the Boston area and found that a whopping 94% of the leases in the sample included at least one unenforceable clause—and all of them had at least one “misleading term.”

Whoa. So, now the magic question: how does this affect you? Wherever you live, there are five key terms that you should make sure are not in your lease before you sign it.

1. Tenant will solely be responsible for damages

The law says that your landlord can’t blame you for bad things that happen because of his own negligence. So if your lease has a clause that says something like “tenant will be solely responsible for damages to personal property” or “tenant will be solely responsible for damages caused by his or a third party’s negligence,” it is unenforceable.

According to the Harvard study, 77% of leases had one of these terms.

2. Tenant is responsible for maintenance or repairs

It is common sense that the landlord needs to pay for maintenance and repairs, but a lot of leases either fail to state this explicitly or try to make it more of a grey area to put the onus on tenants. Watch out for a term that says the tenant is responsible for maintenance and repairs — and then cross it out.

3. Warranty of habitability

In the Harvard research, 70% of leases did not include a term saying that the landlord has to keep your unit habitable. Make sure your lease has this term in it!

4. Tenant has to pay for landlord’s losses if she terminates early

A residential lease may include a clause that holds the tenant responsible for paying the landlord for losses he may suffer as a result of an early termination of the lease (such as the cleaning and repainting costs, loss of rent, etc.). This is often presented as a fee of one to three months' rent.

This term is not illegal, but if you see it, make sure the lease also says something like “landlord must use reasonable diligence and mitigate damages in the case of an early termination.” If your lease has an early termination term, make sure that it discloses the landlord’s duty to "mitigate damages" by accepting a qualified tenant who will pay the rent.

In the Furth-Matzkin study, 71% of the leases included a term that specified how much the tenant had to pay if they wanted to terminate the lease early. Out of these, 84% say nothing about the landlord’s duty to mitigate damages in such circumstances, and only 16% of the leases include a clause which discloses the landlord’s said duty. If your lease doesn’t disclose this, write it in.

5. Subletting isn't allowed under any circumstances

If your lease says this and you live in New York or Illinois, then it is 100% unenforceable. In these states, property law gives tenants the absolute right to sublet, as long as they follow the guidelines for requesting approval for a sublease. If you do that, then your landlord cannot unreasonably refuse you, and if they do — or if they ignore you—you can go ahead and sublet anyway.