they're not all evil, but you shouldn't summon one because they are dangerous. they feed off you during sex which can result in weakened health, illness, lethargic, and prolonged intercourse can result in death. there could be some that won't drain you as bad, or will figure out some partnership, but you shouldn't do it for the main reason it's a demon so if you found a human boyfriend or girlfriend, it won't end well because you are it's food source.
you're young, and probably don't get what you'll be getting yourself into, that being said, i doubt what i said did much, so research them before summoning. be careful what you wish for, and when it does backfire, don't come crawling back asking for help, research it yourself.