So, how do we apply tithe in our modern lives?

Is is argued that Israel was agrarian, but today we are not. Therefore the mechanism of tithing must be reformulated.

Not only are we not agrarian, but today we are NOT living in the promised land. Unlike the children of Israel, we do NOT currently possess our inheritance. We have not been given free land to farm. There are NO Levites. There is no parallel or analogy between Levites and ministers today.

Ministers today buy and rent houses and lands just like everyone else. There is NO difference in this respect. It is true that they work for some church, unlike most of us. It is also true that if a church wants a minister, they should pay for it.

... for the workman is worthy of his meat. Matthew 10:10

But that has nothing to do with land rents (tithe) or inheritances. That has to do with hiring a laborer.

The families of Israel were each "given" a portion of the "promised land" for their inheritance (except for the Levites).

And the Levite, (because he hath no part nor inheritance with thee,) Deuteronomy 14:28-29

The Levites were given a portion of the tithes because they were given no land. Their inheritance was a portion from the other's tithe, in lieu of the land that they didn't receive.

Israel today can no longer claim to be the promised land. You and I haven't been given any land for an inheritance. Our inheritance is still future, so we, like the Levites are Biblically and technically exempt from tithe, lacking an inheritance of land.

If we, today, lived in the promised land, on free land given us by Yahweh, in His rest, we might owe a land rent (tithe) on the increase of that land. "Might" is used because that won't happen until the earth made new, and most of the need for tithe would have been removed. There will no longer be any poor or orphans or widows needing support. There will be no Levites ministering over sacrifices. Jesus and the angels will minister to us, and they have no need of financial support. This author has no guess about the status of tithe in the earth made new when we receive our inheritance.

Merchants at the time of Christ didn't owe land rents (tithe) if they had no fields. Doctors' didn't pay tithe on their income because it wasn't increase from the land. Orthodox Jews, to this day, owe no tithe on anything except increase of produce grown in Israel. (see here)

Likewise, you and I (who aren't farming) have no increase of fields, so no land rents (tithe). Even if we were farmers, we weren't given the land for free.

But isn't income today analogous to income from the fields?

No, an increase in net worth might possibly be analogous to an increase of fields, but income is not.

Income is NOT synonymous with increase. Some part of it may be, if that income is greater than our cost of survival.

Income is an exchange of a portion of life's time for money. There is NO increase, only an exchange.

If you work for an hour for $20, has your net worth increased by $20 if that $20 is necessary to feed and clothe you and your family?

Aren't you left in the same position as before you were paid? You have had income, but have NOT had any increase.

Whatever monetory gain that may be realized is offset by decreased hours of life remaining, resulting in a zero sum.

Tithe, rightly interpreted and brought forward today is this:

God owns everything. Observing Sabbath is an acknowledgment of His ownership and a return of a portion of our time.

Likewise, tithe is a return of a portion of our means.

God allows some to work and earn. This is a gift from Him. Some (the poor, the widows, the orphans) may be unable to earn. It is our duty to help them to the extent we are blessed. They likely will owe no tithe, having no increase.

Many people (the majority) are somewhere between these two extremes - the widows and orphans on one side and the wealthy on the other.

Most people today are barely surviving. They are living from hand to mouth, from paycheck to paycheck.

These have no increase. They are just getting by.

If one earns twice as much as their living costs, they will have an increase. If one earns exactly what is needed to survive, there is no increase and no tithe.

The increase is measured by net worth. We should estimate increase and set some aside each month. At the end of a year we can determine our actual increase. This increase is due to God's bountiful blessings. We will set aside 10% (at least) of our increase and have a great feast, help the poor, the widows and orphans, invite foreigners to a feast and help support the wages of any minister whose services we use.

This is our acknowledgment that God has blessed us and owns us.

If He chooses NOT to bless us with increase, no tithe is due, but free-will offerings will be paid as we are blessed and as we choose.

This author will NOT help support top heavy central church bureaucracy. There is too much spent on administration and not enough spent for ministers, widows, orphans and the poor. There isn't enough feasting and partying. Neither excessive administration nor its financial support are Biblical.