Met a chap in Delhi who had managed to get a rental for 300Rs a day (or maybe it was even 200 ...?). It was called something like Sunni Boni (???) off Desbanda Gupta Rd. But it didn't look like a great bike.
With rental, there is some difficulty with having to confirm with the shop before carrying out any major repairs. Also any non-engine related repairs are your responsibility.
But the quality of the bike is THE main consideration. If you want to get a bike you've rented checked over there is one ace mechanic in Delhi, an honest guy too: Papu at John's Autos, Pandara Rd, just off India Gate.
If you want to buy a bike in Manali around mid-late June, I'm yer man.