Thank You all of you..

A multirotor like this can be seen as a serious security risk by government agencies. It can cause real panic if people find that it can cary payloads of up to 5 kg for such a sustained time. In the RC/ drones debate, one of the best arguments modellers have is the limited flight time and payload capacity and a machine like this would get rid of both limitations. I think that it is important to know the purpose of such a machine before proceeding.

The purpose is only for getting an idea how much it might cost in real world for anyone to get it done.

I like that. !

well,i agree with @SK1701 but we can't force you to tell the purpose so buying or getting it built from a professional would be better as a professional like alishanmao sells these big machines ,so has information about legalisation of such multirotors.
may i know what size of multicopter are you looking for ?,as the one i recommended has more than 5kg payload capacity and 30+ flight time which can be increased by adding a lipo.

I am only studying on what are the possible builds for such a capable system and how many really think it can be built.

with resources and experience anything can be done ,you have the resources but if you need advanced experience in multirotors to build it yourself

ok.. what is advance experience means..

The advance experience refers to the frame design and manufacture(if you're going to make it yourself) , motor sourcing ,  battery sourcing ,advanced flight control board like DJI NAZA,A2 ,WOOKONG - as nothing is made in INDIA and everything is imported and importing -> customs , bribe to customs to release a such a costly and important shipment ....and so on

ok..

i meant if you have alot of experience with multirotors and flight controllers ,like an electronic engineer has knowledge about the electronics  and the knowledge to program some flight controllers like the ardupiolet ,multiwii ,and if you have built several UAV's before you gain alot of experience ,as the first multicopter is considered the hardest one for someone without experience.from how long have you been in this hobby?
regards
rohan

Quite a while...

did u see that idea internet network advertisement juss kidding ( talking quad ) lol bdw if u r serious u can build it ...........

Just talking from Technical Point of View, The biggest hindrance that i see in such a multirotor is "to design a setup which can fly at 1C (including Payload)"
Otherwise, how are you going to get 50-55mins flight time?

Not sure why people are recommending Nano Tech A-Spec LiPo's, when you actually need just the opposite.
Low C Rating LiPo's would be better due to lesser weight when compared to higher C Rating counterparts.

Even if someone is able to design a super efficient multirotor which can hover with it's weight + Payload at 50Amps, he would still need to add in a whopping 50,000mah LiPo (that's 1/3rd of what the battery in your Home UPS can store) which would weight another 6-10KG (6S LiPo)

Basically you need something with AUW 15-20KG with flight time of 1Hr.

Exactly Pointed the facts..

Its possible all you need is a huge battery pack made out of panasonic ncr batteries
Double the cost and half the weight
Using tbs 3-6s lightweight escs
And u8 motors
With a custom made cf frame
Will take around two months of research to get the perfect thing and price can go upto 20 lakhs
But its possible

I have a 40 mins flying copter with a gopro two axis gimbal and video tx

Foxtechfpv`s d130 and k130

I guess he needs 50 mins flight time

Well they offer 7kg payload and 38min flight time.
So if you add another battery of 2kg you can easily bring the flight time to 50min.

Experts please correct me.

I have flown them u dnt get 38 mins

Oh!!! Wow You have flown them.

If this is just to know if it can be built, yes it can. You can get 2-3 hrs flight time 5kg+ payload and require approx limitless budget. Most of the quad will be classified military equipment not available to the public, so you will also need connections to get it. And yes 2-3 months time to design and build it to your specific needs by a expert team of electronics, mechanical and aeronautical engineers.

Bhavesh sir, my bad forgot the batts need to be highly efficient rather than have a high output.

@rcbeil21 thats exactly what i said buy some people prefer taunting then sharing knowledge