Good Faith clause in Late Rent Payment Agreement

[Rowdy B.]

I have a tenant who is late with their rent, but is willing to pay in a short period of time.  I want to be reasonable, but at the same time convey that I am firm about the late payment and ensure future rent payments on time.

I plan to agree to this via a legal document I found online  (I can share the link if you want and if it's allowed) called a "Late Rent Payment Agreement".  This document has a "Good Faith" payment clause:

WHEREAS, the Tenant promises to pay the above amount ($2600.00) owed in full, with a good faith payment of $100.00 cash paid at the time of signing this Agreement, and the remainder ($2500.00) no later than <time / timezone> on <date>.

 I am wondering if anyone has experience using this sort of a document before, and if so, whether a good faith payment is reasonable, and what sort of a percent of the total is acceptable.

I can post the content of the entire agreement if needed, and am happy to share the document if anyone wants a copy.

Thanks in advance,

R