Your queries are relevant to purchase of a flat but are very minimum.
When you are going to purchase 27 L flat or more and putting your hard earned money, you have to be more conscious and safe in your dealing. However, I would like to know whether you are going to purchase flat under construction on in ready building?
Anyway would reply your queries:
1] What are the important points we need to check in the agreement of a flat?
Ans: It is absolutely to go through the Agreement between you and your Builder. However, if you so wish , you may randomly check :
(1) Land is freehold,
(2) Right, title & interest is clear and does not have any encumbrances,
(3) Area of Flat
(4) Amenities provided
(5) Land is leasehold or free hold
(6) Development Agreement.
(7) Society is formed /to be formed etc.
2] How much we need to firstly give it to builder for making of an agreement?
Ans: Depending upon building under construction or Ready building flats
3] What are the important clauses we need to check in agreement?
Ans: at one
4] Suppose, the flat value is 27 lakh then how much would it cost to make the agreement( is there any minimum %? )
Ans : Agreement cost normally depend upon how best it can be executed between parties and normally shared by one or both & will be reasonable. You may contact when Agreement is to be made or write: Jeevan Patil, Property Lawyer : email@example.com; (M) 9869400938.
Pl. note that there are many things among others to check, you may definitely get it done from property lawyer.
ADV. JEEVAN PATIL