(a) Except as otherwise provided in this section, any provision in a lease or other agreement which waives or modifies any provision of this chapter shall be void and unenforceable as against public policy. An owner and tenant may, however, agree to a modification or waiver of some or all of the protections afforded to the tenant pursuant to this chapter; provided, however:
(1) The modification or waiver is encompassed in a written contract which is separate from the lease;
(2) The modification or waiver is voluntarily entered into without duress;
(3) The modification or waiver is entered into with full understanding of this chapter, the terms of any contract to which the modification or waiver applies, and the modification or waiver itself;
(4) The modification or waiver is for adequate consideration.
(b) In any action involving a modification or waiver, the owner shall have the burden of proof to establish that the requirements of this chapter and of this section have been met.