I’m pretty sure a shliach will only settle in a place that has enough Jews to sustain his family. That’s policy. Now you don’t see them all in shul (at least in the beginning) because some of them don’t even know what shul is. Like both my parents never heard of Yom Kippur before they met a shliach.
Many shluchim start off with enough money to last a year, either savings, or now I think there may be grants available. After that they need to fundraise locally. So many shluchim don’t start off renting- they’ll give classes from their house and house the shul there as well. As time goes on and more people hopefully get involved and support their activities, they’ll expand, and keep on expanding with Hashem s help.
@Syag lachochma- I’m sorry if I struck a personal nerve. I should clarify that many of my own friends yell at me that there should not be any such thing as family consideration aka gezhe/ffb vs bt background in shidduchim, and many of the gezhe people believe so as well. Personally it makes sense to me but I should clarify that that’s my personal opinion.
For example the shluchim who mkareved my own father, and are well known and respected throughout the chareidi world, the husband is from a very gezhe family of chassidim from the chassidishe town of nevel, while the wife is herself a baalas tshuva who became one with her on when she was 12 years old.