As long as they're both over 18 in the life you are writing, it's all good. That being said, the dynamic matters.
I started dating someone 39 years older than me when I was 19. That lasted from 2009-2014. I left him because he lied about a lot of stuff, especially his meth habit. He was indulging in it every time I went to visit my parents, and I didn't figure that out until I had a fling with someone who knew him before I did and connected the dots. There was rotten food in the fridge every time I came back from visiting my parents, and meth suppresses the appetite, so the signs were there, but I was oblivious. Also, there was some verbal/emotional abuse that crossed the line into physical abuse at the very end through sleep deprivation when he kept me awake all night yelling.