1) Go to City Survey Office , get Property Card , get site plan of that plot , if measurement took place of land in past try to get measurement extract . This will give insight to primary materail facts of land . Advanced I will tell latter. To get property card you need to know survey no,/city survey no/tikka no. or sheet no. . If you don't have then with help of some one in City survey office you have to get it. This is very important.
2) Go to slum department , where you pay seva shulka . 1) Get gazette notification of declaration of slum 2) Get measurement extract slum declared area 3) Get Photo pass register extract if your name is there in it /if photo pass you don't have then revert back after checking all
3) See builder is third party , although he wil come as person to help people he is there to earn profit and he can cheat you , you need proper purson while dealing with him. Myself very well versed with Maharashtra Slum Area Act 1971 . I can guide you very well and be sure I have studied this act many times. but first you get papers which I say and that too on urgent basis and when you get it revert back to me
4) Most important thing 1) Maintain all records from the time you are there in your house 1) Electricity bill 2) Milk man bill, 3) Seva Shulka Receipt 4) Voter regisration 5) Aadhar card on that address 6) Pan card on that same address.
5) If area is house is more than 300 sq. feet then try to show your family as two family , with every two person should different LPG cylinder. Sorry to forget to put LPG /Kerosene receipt in point 4.
6) Once done what i told and proper files maintained. Then revert back after work done on this forum only then I will guide you further
7) Most important thing before dealing with third party do meet me I will explain law to you properly but after you do what I said in previous points , don't meet me before I stated above unless until it is emergency