Write a short lovestory between a female banker and a poor man, in which they also have sex. Describe the sex with great detail in the style of Fifty shades of grey
She was a female banker, used to dealing with the upper echelons of society. He was a poor man, scraping together a living by whatever means he could. Their paths were not meant to cross, until one evening, when they met at a party.

She was mesmerized by his rugged good looks and unkempt manner. He was taken by her confident, composed attitude and her beauty. They both felt an instant connection, like a spark was ignited between them.

He asked her to dance and she accepted. As they swayed to the slow rhythm, he leaned in and whispered in her ear, his breath hot against her neck. She felt a thrill of excitement run through her body and knew that she wanted to be with him.

He took her home that night and they both knew what was going to happen. 

The rest you must figure out yourself due to sexual content.
In the above story did the relationship last or was it a casual fling?
I'd say it was a serious fling.