go to www.mtmis.excise-punjab.gov.pk/ and verify the detail of the vehicle....get a TO form from the seller along with the other Documents( Registration book and Return file)...it has 30 days expiry period...i don't have exact idea either u can transfer the ownership of lahore number from bahawalpur or u ll have to come to lahore...
the charges are:
1200 for transfer
1200 for number plates(in case u don't have computerised number plates)
500 for passport book(if already exists then u have to pay sticker price, 200 rupees i think)
300 for TO Form as i said earlier(seller should pay for that)