In his experience, he suggested three.

In California 'ya know PG&E downed power lines caused fires.So there's those three things to ding the value. 

Three appraisers will all measure a different size.....no two are almost ever alike.If you end up buying this house, I would update the size with the appraisal district to potentially lower your taxes.There can be lots of discrepancies in sizes....every appraisal will likely have a different size, builders plan could be different, tax roll can be different.   

But don't worry, the city is nice enough to give you three options to cover this cost; 1) you can have it spread out over a number of years in your property tax bill, 2) they will give you a short term loan to finance it for you, or 3) you can pay it in full when you purchase or build your home. 

I have just started to learn about real estate investing in the past three months.

We keep track of property expenses - all maintenance expenses, improvements, and business expenses, as allowed in the tax code (like a subscription to Wall Street Journal and lunch with other investors). 

I am under contract for a duplex in Syracuse, NY, built in 1925 and have received three different insurance quotes; all having significantly different dwelling replacement costs.Purchase Price: $155,000Quote 1 - $292,000 (premium: $1,062/yr)Quote 2 - $400,000 (premium: $1,072/yr)Quote 3 - $600,000 (premium: $1,264/yr)I chose the $2,500 deductible.How do I know how much I will need?

The wiser option would be get the property to strictly rent it out completely since I am searching for at least two to three family multifamily.Im not sure if this will work but here is the link to the analysis I did - https://www.biggerpockets.com/...

We'll start with the glaringly obvious...Lead sources for WholesalingThose three that you mentioned aren't going to be enough. 

If priced right, the seller can expect to receive multiple offers within the three day period.