Masjid and Jamaat khana

A Jamaat Khana is a place that is used to perform salaat therein, one Jamaat or many. No need for Jumuah or Itikaaf to be performed therein, no need for it to be on "wakf" land.

Jamaat Khana should be built or house used for /as Jamaat Khana, then once it is well used and over flowing, then that indicates that the locality now requires a Masjid, thus then construct a Masjid.

As I understand that if there is 40 Muslim families in the area/locality then they should have a Masjid, which should be simple and easy to maintain.
Second Jamaat Salaat in the Masjid is Makrooh, there is no sin if 1 or more salaats are left out in the Jamaat Khana. If done so in the Masjid, then this is sinful.