Other than Abraham, where is a 10th required by every person/individual? Where is the 10th of anything mentioned except for offerings/sacrifices? Now there is a bi-annual ‘first fruits’ , however, it does not say anything about it being a 10th. Can you please direct me to the passage that speaks specifically about every person/individual is required to give a 10th of all they earn to the Levites? As far as I know from the daily study I do, there was never a time when all were required to give, every person 21 and older, Ex 30:12-15, however, the amount required was not a 10th, it was a half shekel ... v. 15 “The rich does not give more and the poor does not give less than half a shekel, when you give a contribution to YHWH, to make atonement for yourselves. And notice, it was a one time contribution for atonement, it was not an annual event.
As for the Levites who “also checked buildings for contaminates, inspected people of illnesses, etc.,” this was all part of their duties as priests so to keep the land & the Temple from being defiled and thus God had already accounted for this in the bi-annual first fruits & tithes or the weekly sacrificial offering some chose to bring. There is no mention that I can find in all of the Pentateuch that says the tithe must be a tenth of all. There is the 10th animal, there is the 10th of an ephah of grain, or a 10th of a hin of oil, however, where is the 10th of all that comes in that you are speaking of because it certainly is not associated with the passage that speaks of the rich & poor give the same amount.
As for the Levites checking buildings for contaminates, etc., yes this was part of their priestly duties. But it was also meant to keep the people clean hygienically as well as spiritually. Those commandments were given for their benefit just as much as they were for God's holiness.