Your objective in renting a property does not change if you decide to do it on your own - you want to find a reliable tenant with good credit and the means and commitment to pay you the rent on time and in full for the term of the lease. What does change is the exposure and assisance you will have in reaching and securing that tenant.
You mention lowering your rent if you do it on your own - why would you want to do that? An agent will help you determine what the market rate is for your property and rentals are strong now, so you should try to get the most the market will bear. That is what we do for a living, whether we are assisting landlords or sellers.
What you or the tenant pays comes in the form of commission which is generally equal to one month's rent and that can be paid by landlord, tenant or split between the two in some fashion. So if you do it on your own, that expense will be saved,
But you will work for it - yes, there are places you can advertise, some for nothing - like Craigslst. You will have greater reach through the syndication efforts of a broker - there is no disputing that. And it the more people you reach, the greater your chances for success.
No matter the appproach you take YES, you should use a contract and take the same care in evaluating a possible tenant that you would if you were enlisting the support of a tenant.
Good luck to you,
Unwavering Commitment to Service, Unsurpassed Results