Hi
Y can register a tri -party agreement by including builder as the first party , X second party and the Y third party the purchaser.
The document ask for verification are the
1. Title deeds of the land
Sale deed in the builders name,conveyance,
Builders document:--------
developmental agreement if he has no title of conveyance or sale deed in his name
Partnership and power of attorney if any in case of a firm
Commencement certificate, completion certificate,,possession certificate etc.
Khata certificate & extract from BBMP
latest tax paid receipt
If any loan outstanding on the property, latest statement from bank
Encumbrance Certificate from date of purchase till date
Agreement of sale & construction executed by developer in favour of seller
Latest electricity bill & receipt for the said flat
NOC from Apartment Association if it is registered under the association
Sanctioned building plan
Possession/occupancy certificate from builder
All title documents of land owner
Joint development agreement, GPA, & Sharing/supplementary Agreement, between land owner and builder
A Copy of all registered previous agreements (in case of re-sale property)
RTC (Records of Rights and Tenancy Corps) or 7/12 extract
Conversion Order issued by the concerned Authority
It is advisable to find a lawyer from the area where the property is located