Make sure your agent communicates the reasoning why your offer is low (extensive renovations are needed, place is old, layout needs work, building permits needed, etc.). 

@Melonie DicksonI’m a Realtor and 99% of the time I strongly recommend an inspection for all the reasons these commenters have stated.

Our CPA Tax guy in Covina, California is reasonable and specializes in Real Estate. 

If there are other properties renting in the area, there is no reason for a 4 month vacancy.

We are converting our house into a rental property and there is an interior security camera (part of a NEST system) in the main living area Is there any reason I have to remove it when tenants occupy the property?

What’s the best way to ensure that the price they are charging me is reasonable and how can I hold them to the work/schedule/costs estimated to me?

Perhaps see if your landlord would be willing to do a lease-option with you (assuming he'll sell at a reasonable price).If the owner is an investor, ask him to lunch and talk to him/her about how they got to where they are. 

I have pulled all county information on each property, analyzed the area and it seems the reason the taxes were not paid is because the owners are Heirs, so they obviously cannot care.

If you're expecting $100k net in year one it's well worth it to add a tax CPA/EA to your team of external partners.An LLC with an S election might be the most advantageous avenue to pursue.You would have to pay all employee-owners 'reasonable compensation'. 

They are a big operation, but seem reasonable.