As long as everyone is open and honest about what they're doing and what they truly want I think they can "Benefits" can be wonderful and deepen a friendship but if they're not ready for the emotional developments or for losing those benefits when a true "+1" is in the picture is can get difficult

💯

It can work, but as with all things, needs to be clearly communicated - especially if other friends/partners are involved

I think if it's a newer friendship and all parties involved are on the same page as far as it being just casual then yeah.

I believe so

Depending upon the friendship, then definitely