Online dating scammers looking for money, not love. I have experienced this in the past as well. The most popular thing is someone saying that they saw your ad on a dating site and they find you incredibly attractive. If that isn’t a red flag, I don’t know what is.
Then they usually write you so much detail about themselves and ask you to contact them back. An attractive and often revealing photo of themselves is included and they act as though they are local to where you live. Spelling and grammar is usually bad and other obvious errors show.