You want to make money? Write tropes.
What is a trope?
A trope is an expected story line. In romance, it's usually how the couple meets/falls in love and is the type of relationship explored. It is possible (and encouraged) to combine tropes to create a unique take on the familiar.
Romance readers love tropes. They have their favorites and will search them out. As a writer, you can use this. If you give them what they are looking for in your story, your readers will love you. If you can hit the beats of the trope, the parts that make the story resonate, then you'll find success with your readers.
Can you be successful not writing these beloved story lines? Sure. It happens. It just doesn't happen very often. Take a look at the best selling books and I can guarantee you'll see some form of at least one of these tropes. Human beings like the familiar. We like knowing what our stories are going to be, especially the ones we're reading for fun and relaxation.
If you want to make money with
-Childhood Friends: couple starts as friends that mature into lovers. I include “best friend's sibling” in this, as the sibling was a friend that couldn't be a lover until now. (Example: Beautiful Disaster)
-Second Chance Romance: a long lost love returns and they have a second chance at love. (Example: Champagne Kisses)
-Forced Proximity: something forces our couple to spend time together. This can be weather (blizzard traps them) or social (must go to wedding together). The couple has no option but to be around one another and thus fall in love. Works well with enemies to lovers. (Example: Hurricane Kisses)
-Fake relationship: Couple pretends to be together but ends up falling in real love. (Example: Pretend You're Mine and The Wedding Date)
-Secret Baby: there is a baby, but no one can no about it (not even the father of the baby!) (Example: Forever Kind of Love)
-Arranged Marriage: Usually found in historical romances. It forces the hero and heroine to deal with each other. (Example: Highland Surrender)
-Billionaires: Modern day “princes” that can sweep women off their feet. Their money makes it difficult for them to find love. They can buy anything but love. (Example: The Kisses Series)
–Mafia: bad boys who are dangerous and the innocent women that love them. This is basically beauty and the beast tropes. (Example: Crime Boss Baby)
-Forbidden love: For whatever reason (political, racial, class, societal, or species) the two characters cannot be together. (Example: Romeo and Juliet and Stepbrother Hero)