Past service can't be an asset. You can convert your present service into assets (i.e. you can save instead of spend) but the compensation for the service itself can only be done at the time it's rendered, even if the payment takes the form of debt. But the debt is the asset, not the past service itself. And I don't see anything wrong with that. It is quite literally the essence of capitalism.

Rent-seeking is different. Rent-seeking is the act of growing one's existing wealth by manipulating the social or political environment without creating new wealth [1]. That is not at all the same as making your living off of assets that you've earned with past labor.

[1] https://en.wikipedia.org/wiki/Rent-seeking