"I don't want to live with someone who is capable of doing that "
Then you'd better not live with anyone.
We're all capable of falling in love if the right circumstances (and person) present themselves.
I find the idea that there is a "cheating type" and that if you are not with one of them your marriage is at no risk of infidelity extraordinarily naive.
Is it a relationship version of the just world fallacy?
People say things like "if he's going to cheat, he will" as though all people who cheat are habitual, serial adulterers.
In fact people have situational affairs all the time. They don't want an affair with just anyone, but meet someone that piques their interest in a situation that makes it natural or easy for an intimacy to arise that is a threat to their primary relationship.
Nobody is saying that a man and a woman sharing a house will definitely shag.
But neither can anybody say that there is zero chance they will fancy each other. They might.
And if they do, and they are sharing a flat just the two of them, the chances of that spark leading them astray over time are not negligible.
Long distant relationships are hard to maintain because your level of intimacy is not constant - it fluctuates when you don't see each other for extended periods.
To live with another person of the opposite sex, in many ways as husband and wife (sharing a home, chores, meals, evenings relaxing, nights out) when you are far away from and missing your real spouse strikes me as incredibly foolhardy.
A mixed gender houseshare with more than one person would be different.