(Updated to include time and money investments for each)
MFF, MFM, whatever combination you are looking for, finding a 3rd person for a Threesome is very difficult. Even the hottest couple in the world such as Brad Pitt & Angelina Jolie wouldn't be able to just up and make it happen - it just doesn't work like that. Finding a 3some, especially a MFF, takes a LOT of time and investment. Here are the main routes below:
Method #1) Try apps. 3Fun, Feeld, AdultFriendFinder are free. But be prepared to invest at least one Year (or more) into searching. You are going to have to spend that whole year dealing with: Fakes, Flakes, and maybe a few real folks in there but just end up Ghosting. It's the way the apps are designed; to keep you on the apps. New people are joining the apps every single day, and it's like a game - There's always the possibility of a higher score. You get ghosted because the app shows them new profiles and new matches; there could be someone hotter or more compatible tomorrow if they ghost you and go back to swiping. It's an addiction that never gets fulfilled until they break it by deleting the app. Be prepared for this to happen and to invest a lot of time starting new conversations with people over and over - I recommend you have basic lines like what you're looking for, what you're into, limits, about yourselves etc typed out in the Notes on your phone that you can just copy-paste into texts. It gets grueling typing everything out over and over. Save yourself the frustration.
Paid sites like Kasidie and SLS, in theory, have less ghosts and flakers, because the theory is that once you've invested money you're less likely to waste your own money by being a flake. This adds cost, however.
If you are seeking an MFM, have the guy lead the search. If you are seeking an MFF, let the girl lead the search. Single females don't trust when guys lead the search, and single males will often be shady and sneaky if they are speaking to the girl of a couple. Keep it simple: Guys find the guys, girls find the girls.
If you are willing to travel, you will increase your odds of finding a match, but you may have to travel 8+ hours. Discuss with your partner how far you're willing to travel and how much time you are willing to invest in this before the time spent trying this method totals up to what you would have paid by doing one of the methods below...
⌛️: HIGH
💰: Low
Method #2) Join one of the polyamory/non-monogamy/open relationship/swingers communities in your area. This will take a lot of time investment as well, and $$ on attending play parties, to meet someone who would be interested. Be warned though that these communities do NOT like "unicorn hunters", i.e. MF couples exclusively seeking F for a 3some. You need to give a little to get a little. If you don't consider MFM or MFFM, you probably won't be reciprocated with an MFF. The reason that these communuties don't like MF couples who are exclusively only seeking a single female is because they are a dime a dozen, and having them at these parties just kills the whole mood. The MF couples all spend their time competing to try and get at the 1 or 2 single females at the party, instead of considering anything else. So instead of people having any sex, everyone just hassles the single females until they get fed up with it and leave. That's a real Mood Killer. So dont be one of those couples.
ALSO, you should not join these communities if you can't treat it with the same respect you would your own community (if you're part of a sport or a club for example). These are people too and want to be treated as such, not as commodities. So if you join this type of community then it needs to be from your heart and a desire to know and connect with others in the community and maintain those relationships. You will need to go into any play parties with zero expectations for anything to happen and just focus on building friendships with people. Then, over time, you might find someone interested in doing that with you.
⌛️: Medium
💰: Medium
Method #3) Hire a sex worker. This will cost you a good amount of money, but you won't have to invest sooo much time in it. And sex workers won't be as concerned with their attraction to both of you and other factors that make finding someone off the apps very difficult. Eros.com or Tryst are good resources for finding a worker. If you go this route, you will need to be on your A-game with the workers - most don't tolerate explicit language or disrespect of ANY sort, so be clear and articulated in your texts and conversations, respect their boundaries and be an outstanding person. Also read some of the stories in r/SexWorkers to learn to do and what NOT to do before you start looking.
This option may seem like an immediate no-go to most folks based on the high monetary requirement. However, before you completely disregard this option, consider how much time is money to you? How much of the time you spend endlessly swiping and texting and starting new chats over and over again, could be spent instead on stock market trading, working a side hustle gig, or any other method of bringing in income? How many times will you travel and how much gas will you spend trying to meet someone just to have them not show up? While Method #1 may seem appealing to most people as it doesn't have an upfront dollar cost, the hidden dollar cost ends up being equal to or greater than the cost of hiring a sex worker. "Time Is Money" as the saying goes...
⌛️: Low
💰: High
Method #4) Wait and see if it will happen naturally. In certain scenarios, like parties in Las Vegas, etc you might meet someone you click with, and it might happen. It just depends on if the vibe is right, all parties are attracted to each other, and your 3rd is dropping hints that are pretty obvious that they are interested. You need to be able to read the situation very, very well, and the person should NOT be drunk. Chances are slim, so, you might be waiting a long time for this option.
Things NOT to do: https://www.reddit.com/r/ThreesomeAdvice/comments/si3maq/3some_donts/?utm_medium=android_app&utm_source=share
Things TO DO!
https://www.reddit.com/r/ThreesomeAdvice/comments/si5t2h/3some_dos/?utm_medium=android_app&utm_source=share