Start first with a tavern that gives a serious discount . 1 gold piece for say a weeks bed and breakfast .What else should a place have to make players want to visit regularly and get to know the people?
A temple that heals for a reasonable fee say 100 or even 200 per level raise dead fees ?
Make your hub town more Barbaric and have some sort of fighting pit or arena with prizes . Players can take part and not even leave the town .
Have the players take part in some sort of competition and the win a house as a prize . Players love playing house in down time mode . Pull off a home schematic off the net and give it as a handout. dont just say you won a house , give em a house map.
Have them join some sort of town faction eg. Militia , gang , merc unit or heck adventurer guild .
Quirky or strange but interesting NPC characters are excellent and keeps em rooted . I am sure some sort of "Princess Zelda" in distress npc helps . Everyone wants to be Link .
Last but nasty idea . Remember this is one for all and all for one . Start fishing with "relationship" bait .
One player falls in love and "marrys" , DM owns him . "Wifu" does not want to move to another town . Player is stuck which means all his buddies are stuck too .