In the journey to Holiness and Godly Love, we almost all start out with this kind of “reward” mentality. We even refer to it that way as in, “He went to his Final Reward.”
The myatics of the Church, (Francis DeSales, Catherine of Sienna, John of the Cross etc.) all dealt with this in one degree or another.
We begin by turning away from sin, accepting God, praying and getting our life in order. While we are doing it for Love, tht Love is often a servile Love - Savish fear - Fear of Hell or desire for heaven.
Next as we grow in our Journey, continuing to pray and rooting out those deep sins our Love growss stronger. Both our Love of God and Our heighbor. But it is still a “mercenary Love” (servise of God motivated by reward)
In the higher stages of development our Love becomes a “Spousal Love” or Filial Love. In this stage we are “ruled by Love”. Even Love of our enemies. Love of God as a very Dear Friend whom you would never hurt under any circumstances, not because of reward or punishment, but because of Love.
If you would like to pursue this an excellant book is “
The Fulfillment of All Desire” by Ralph Martin.
I promote this book so much I should get a cut


.
Seriously though it is an excellent read and will answer your questions on this subject.
Peace
James