Ultimately, vetting is about uncovering “Red Flags”.
Red flags do not imply people are not good people. It only suggests concerns about the likelihood of a good fit between exchange partners.
You are looking for open communication that clicks with you and resonates with them, too.
You are looking for commonality of the important things. For example, if you are non-smokers and they are not and they smoke in their home (as is their prerogative), you may not be comfortable staying at their home. That is particularly true if you have a medical condition that residual smoke exacerbates.
If you are allergic to cats and your exchange partner has three of them, that is certainly a red flag! Chances are the exchange won’t work for you.
Are they forthcoming about their information; their home, their circumstances and their level of mutual disclosure? If not, there may be an issue between you and your exchange partner for whatever reason. In such cases, you may want to consider whether you are trying to put a round peg in a square hole.
If your potential exchange partner’s home requires access to three floors (like washer & dryer in the basement, kitchen on the first floor and bedrooms on the second floor) and you have trouble walking up and down stairs on a regular basis, that home may not be a good fit for you.
Is your intent in exchanging to have your family or friends visit while you are at your exchange partner’s home? If they are not comfortable with that arrangement, you have a potential conflict.
In the end, red flags can be big things or they can be minor things. The less of them you have between you and your exchange partners, the more likely the success for the both of you. In such circumstances, you both will more likely enjoy exchanging your homes and experiencing your respective localities.