Riding Motorbikes in Hanoi... Risk vs. Reward

I will try to give you some answers:
1) You dont need a license to access petrol/maintenance here in Vietnam. All you need is money and ... a bike.

2) For Vietnamese, it varies from VND 100k to 300k depending on your negotiation skills. Sometimes when polices are in of arrest campaign, you have to go the station to pay your fines and collect license. I dont have any info on fines for foreigner getting caught.

3) In my experience as a Vietnamese, foreigners are not normally get caught here in Vietnam as long as you dont violate the rules seriously.

4) I would advice you to go to patrol stations to buy genuine insurance. But whether or not the insurance works is another story  in Vietnam.

5) Some pros and cons of motorbike ownership
+ Pros: Motorbike is by far the most appropriate means of transport in big cities like Hanoi or HCM city (I lived in them both) given the current situation of transport and infrastructure.
            When you get used to Vietnam, it can be recommended to take motorbike trip to other provinces of Vietnam. There are nice places near both Hanoi and HCM city.
            You dont have to invest a lot to have one.
+ Cons: The main one is that traffic in Vietnam is terrible. It will take time to get used to it. You may be shocked or it is even dangerous for you to take part in it at first.
              Air pollution (Terrible as well)
              Thief
              ...

Conclusion: If you plan on living here for a long time, you will have to use motorbike. There is no better option out there really. So learn things and give it a try.

                      I highly recommend you to get a license and insurance here before start using motorbike. It is not so difficult to get one especially if you have trusted Vietnamese friends to help you work on paper work.

Best of luck.