Sounds pretty normal especially for fantasies. But even in real life quite large age differences are not something to raise eyebrows over, you're 18 so you're young but not a child anymore. However I think there is something to be said about age differences. What matters in my opinion isn't the years since you we're born but the years spent as an independent person. A person aged 40 (often) has much more than twice the life exoerience of a 20 year old since a 20 year old most often has barely left their parents home and has not had much time to learn to be truly independent yet. The learning curve is very steep in the beginning, flattens out considerably later on and there is a large amount of individual variability, so a mature 25-year old can definitely be on equal terms with a slightly immature 50-year old, but it is hard to say the same thing about an 20-year old 1/3 a 40-tear old, no matter how fast of a learner the 20-year old might be.

You need to be a bit extra careful with people aged 30+ choosing partners that have very little experience of being an adult and making grown-up decisions (eg. younger than say 21-22). I'm pretty damn openminded about these things - but I think someone should spend a few years as an adult before they get involved with people that are much older than themselves. I think most psychologically healthy older people worth their salt would see the need for and the value in letting someone to establish themselves as independent adults beforehand so they can truly relate to them as partners in a relationship and not as dependents. My point is not to call foul on anything else, but that you should be aware that quite a few of the older men looking for very young girls probably aren't well balanced and emotionally healthy. Most of the good men that I know in the 30-40 age range would strongly prefer a girl to be a bit over 20 at least.