Help in buying a DSLR and lens?

Since my last question is a little misunderstood here I go again.

I want to buy a DSLR which can shoot good low light images and have fast shutter speed.
I'm looking at Nikon D5100.
Maximum I can shell out is $800 (Rs 45000) this is for DSLR body only

Regarding lens my budget $444 (Rs 25000)
I mostly shoot Portraits, Building and architecture, Landscape.

Please suggest most Value for money DSLR and lens.

Ok you have a little problem there because you've just asked for 2 different lenses.there's no such thing as a do-all lens. If you want portraits, get focal length 85-135mm.landscape and buildings will require something along the 8-15mm range. So you either have to choose a cheaper body or save up a little more to get 2 lenses. Rokinon makes tack sharp lenses if you don't mind manual focus.

Get the d5100 with a 50mm 1.8 and a 18-70mm

Portraits, architecture, and landscape don't necessarily call for low light capabilities. Also, portraiture requires a different focal length than the others you mention. D5100 is a fine camera body, and I'd go for a 50mm f1.8G AF-S lens for portraiture. An 18-55mm kit lens will be fine for the rest. Use any remaining budget for a decent tripod. It's essential for architectural and landscape.