In addition to credit and income requirements, many landlords also require that, before or at the time of signing a residential lease, each prospective renter pay not only the first month and last month's rent and a security deposit that is usually equal to one month's rent.

(A) pay not only the first month and last month's rent and
(B) pays not only the first month and last month's rent and
(C) pays not only the first month and last month's rent, but also
(D) will pay not only the first and last month's rent, but also
(E) pay not only the first and last month's rent, but also

Solution:
Idiom is ‘not only…but also’

So eliminate A & B
C – first month and last month’s – not parallel
D – when using ‘require that’ only plain form of the verb- ‘pay’ needs to follow, ‘will pay’ is wrong
Leaves us with E.
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