What you need to know:
1. Do not assume you or your partner is into this.
2. Talk, at length, beforehand. Take the time to speak on every aspect
-gender of third
-boundaries-if at all
-long-term or short-term
-communication, communication, communication
-what you will tell your neighbors
-Is this legal in your state, area, country?
This is just a few things to speak to your partner about before walking flown this path for sure. If you feel like you are being convinced or coerced, you do not have to consent, state your boundary and be willing to leave if it continues. Spread love!