Customizing for Loans (microcredits)

Customizing for Loans (microcredits)

Hi, 
I'm interested in using Zoho for our company.  We are currently evaluating several options (Salesforce, Openbravo, vTiger, and SugarCRM).  Although there are a few things I don't yet understand: 
In our company, we give out individual loans to the people in a group, which they have to pay back in twenty weeks.  All of the women pay together (they'll deposit the accumulated payment together) each week.  
We want to use ZohoCRM to keep track of the payments and loans (how much each group is supposed to pay each week). We also work with some companies where we finance the acquisition of catalog sale products and need to keep track of inventories.  How would we be able to use Zoho CRM for these situations? Would we have to customize it from scratch? And would it be an extension of the CRM module? Or would it be a separate module?  
Or would this be done through Zoho Creator? 
The problem I see with Zoho Creator (and with zoho CRM in general for this) is that I don't see any option to detect when a payment would be late (it seems very limited in things that can be done).  
So, would this be possible in Zoho? Or is zoho not biult for something like this? 
Thanks, 
Daniel