Do I need separate inspectors for property and pest inspections?

Not when dealing with Grounds Home Inspections.
David Grounds is a Certified Building Inspector, a Certified Pest Inspector, a Certified Pest Controller and a Registered Builder
Some may tell you that you need different inspectors but in reality you will get a higher level of inspection if the one person handles all aspects of the property inspection. For example, a dedicated pest inspector may be inclined to push you towards unnecessary chemical pest treatments to generate sales. Or a house inspector may not be aware of the dangers and hazards certain pests may have upon a buildings structural integrity.
Many inspectors do not have this cross inspection knowledge.

“Can a property fail an inspection?”

Short answer, No. A property can not “fail inspection”.

Long answer… A home or commercial inspection is an examination and assessment of the current condition of a property. It is not a ‘market value appraisal’ or a ‘council compliance inspection’.
A property inspection will give you a detailed run-down of a properties condition, indicating what may need to be repaired or replaced. However, a good, unbiased, independent inspector will help you make the right decision in determining if a property is worth your time and money. I suppose that is the true indicator of whether a property has ‘failed’ an inspection or not.

“Can you quote on renovation costs?”

Due to costs greatly fluctuating from one builder to the next due to methods, materials, designs and tastes I can not quote a client on repair or renovation costs.
However I do give clients a detailed estimation of cost and time within the inspection report of any work which may be required.
I remain independent of builders and real estate agents and endeavour to serve the best interests of the client, offering unbiased assistance well after the inspection has been completed.