Most tenants will likely have a cellular phone line that comes with them. If that works for them, then great. However, if the tenant was to need a telephone line, then they can look into SIP? or VOIP? solutions. Unless the building covers the telephone service, I will imaging that Callcentric, and Voiply as good choices. Voiply will provide you with an ATA? since they don’t support open SIP standards.