There are many men and women opting to be friends with benefits. People want the non-commitment relationships, where they get to have fun and hangout and gain sexual enjoyment at the same time. Once you find someone you want to have a FWB relationship with and get into a rhythm, everything is great. However, you need to ask a girl to join in with this idea first.
A text message is often the least nerve-wracking way for many. You don't have to see their reaction, but instead just read their response. It also keeps the whole relationship casual, the way you want it.
To some girls, a text can be initially offensive. That's why it's important to word it well. You want to get the right message in your words, so you're fun and flirty while keeping it all as casual as possible.
This isn't something you can do with all girls. There are certainly some who will prefer a face-to-face chat, whether in person or over something like Facetime. If you've found someone through a FWB dating site, they'll be receptive to the right text message.
Rather than going in with a question, the best way to get a friend with benefits through text is by making your own intensions clear. Rather than stating that you want sex with no strings attached, word the text message in a way that makes it clear you're not interested in a relationship. This could be that you don't want a relationship with this particular person or the fact that you're not interested in a relationship at all.
Leave it open for the girl to decide. Instead of asking if she's interested, making it clear that the ball is in her court. Try this sample text message:
"Hey X, I really like your profile pic/really like spending time with you. Right now, I'm not interested in a relationship because [insert reason]. But I'd love to see you more and enjoy our physical chemistry. If you're not interested, that's fine. Either way, just let me know. No hard feelings."
Keep the text honest, but avoid any guilt. You want to make her feel comfortable in giving you an answer either way.
You won't always get a "yes." Sometimes you'll get a maybe that you can turn into a "yes" and other times you'll just get an outright "no." Or you may even get ignored. Whatever the reply, be respectful.
Once you do get a "yes," it's time to set out the ground rules. All good FWB relationships with have ground rules, with one of those touching on what to do if one of you starts to have feelings for the other. What will you do then?
You can ask a girl to be FWB over a text. When you do it with the right message, you stand a better chance of finding someone interested in the same thing.