Yes, you can create your own lease agreement without the assistance of a lawyer or other professional.
Can you write your own tenancy agreement? Certainly. Unless you're an attorney, or have an attorney review it, you probably shouldn't, But you certainly can. If you fail to follow your state/local laws to-the-letter, the agreement may be invalid.
You're bound from the moment that you agree to rent the premises. This means that unless the landlord lets you out of it, you can't get out of it.
Handwritten contracts are legally binding if they meet the necessary conditions that apply to all contracts: mutual agreement, capacity, consideration, and legal validity. There are no legal differences between typed and handwritten agreements when it comes to enforceability.
Lease agreements are a contract. But you don't necessarily need to hire a lawyer to write good lease agreements, you can do it yourself. But you're a first-time landlord or simply don't have the time to write a lease, you can hire a property management company to do it for you.