Guide to Renting or Buying  
          String Instruments
For beginning string students, deciding whether to rent or buy an instrument - and then actually choosing an instrument - can be a challenging task. Here's what I recommend:
Who Should Rent:
1. Someone who wants to try out the instrument without an upfront financial commitment.
2. Someone who wishes to play a higher quality instrument than they could afford if purchasing.
What to Keep in Mind:
Renter's Insurance: Renter's insurance is always a good idea - the best kinds are full coverage plans for an additional fee each month. Be sure to ask your instrument renter what they offer - some music stores require that your instrument be covered by your own insurance (homeowner's or renter's) which may not be helpful if you have a high deductible.
Flex Plans/Rental Credit: Keep in mind whether or not any of your monthly rental fee counts toward an eventual purchase.
Instrument Quality: Many small music stores carry subpar instruments which they rent for the same price as better music stores. If you're renting in the Bay Area, I recommend Ifshin, Lamorinda Music, or Shar.
Buying an Instrument:
Purchasing an Instrument can be a rewarding endeavor - after one upfront financial commitment, there are no monthly fees - and your instrument can potentially be resold for the amount you paid when you no longer need it or wish to upgrade.
The number one rule of purchasing an Instrument is: BE CAREFUL (!) - as a teacher, I have seen some of the worst instruments available - many, many businesses profit from selling extremely poor quality string instruments to those who do not know better. Always avoid: Ebay, Amazon, large store chains, and most often anything that would come up from a general google search.
The second rule is: Always make sure you can try out the instrument before committing to purchase it - this way we can decide together whether or not the instrument is right for you - and will allow you (or your child) to enjoy learning to play. 
My Recommendation for Purchasing:
For beginning Instruments, I have found Shar Music to be the best for the price, time and time again. While they are not located in the area, their flexible trial plans and relatively low shipping fee (which is credited to you if you buy) make purchasing a decent quality instrument an easy task. If you're not totally sure about buying - Shar also has a great rental plan which allows you to try out an instrument while accumulating 1/2 the rental fee toward purchase. And no, unfortunately Shar is not paying me to say such good things :)