better u buy a good one. anyway they will charge for wifi and are going to take it back if u disconnect connection.
if u change u r connection also never mind u still own u r router.
wifi router cost ranges from 1300 Rs to 4500 Rs.
choose a router which has dual antenna (for long range), with N series support(more speed & future proof).
the high end router has built in modem.but u dont need that becoz BSNL or any ISP will provide that for free.
so best price will be 2000 Rs to 3500 Rs
top brands are Belkin,Dlink,buffalo,Netgear,Linksys.
I use Belkin with dual antenna with N series 300mbps,5 years warranty and i bought it for Rs 2900 3 months back.
You can try a rental option then purchase it here in the attached file that various types of modem and its MRP is given along with the manufactures..even the vdsl for 16Mbps connections are given.