Those without their own livestock or crops necessarily could not tithe according to the law. The method by which debts were settled is irrelevant to the thread topic.
Let's try Deuteronomy 14 again....
22 Be sure to set aside a tenth of all that your fields produce each year. 23 Eat the tithe
of your grain, new wine and olive oil, and the firstborn of your herds and flocks in the
presence of the Lord your God at the place he will choose as a dwelling for his Name,
so that you may learn to revere the Lord your God always.
24 But if that place is too distant, and you have been blessed by the Lord your God
and cannot carry your tithe (because the place where the Lord will choose to put his Name
is so far away), 25 then exchange your tithe for silver, and take the silver with you and go
to the place the Lord your God will choose.
26 Use the silver to buy whatever you like: cattle, sheep, wine or other fermented drink,
or anything you wish. Then you and your household shall eat there in the presence of the
Lord your God and rejoice.
Israel was essentially an agricultural nation. (Land of milk and honey).
And, from what can be gleaned from what is written in the law?
It appears that the laborer would most likely be one of the foreigners who were often mentioned in the law.
Foreigners were not commanded to tithe.
However, foreigners (also Levites, fatherless and widows) who resided in Israel were beneficiaries of a specific tithe called the "poor tithe" or "third tithe"
Deuteronomy 14:28-29 and Deuteronomy 26:12.
The Jews did not have a government issued currency.
But rather, pieces of silver that were carefully weighed and stamped as a means for exchange.
So, silver would be used instead of produce from their flocks as a perfect substitute.
grace and peace ...........