The requisite to join the Lord’s Alliance faction is to be a local resident.
To become a member of the Lords’ Alliance faction in Waterdeep, a character must be a Waterdavian citizen. Those with criminal records can also join, provided they demonstrate their allegiance to the city.
After Dragon Heist’s 2nd chapter, players receive the deed for Trollskull Manor. Do they now all qualify to join? Or is the intention here that players had to be prior residents, based on the background?