So it's best to control the situation than be surprised

It was awful.Went to Costco and purchased lots and lots of white vinegar and poured it on the rugs all over this got the carpet pad also, let it sit over night and came in with a rented rug doctor and was surprised,   No stains  No Order carpets looked new again 

Don't be surprised if your offer isn't accepted because of a walk through contingency.

Just don’t want to have an unexpected cost that could turn a good deal into a bad deal.

It all depends what you can afford and the area you are investing. 4 fam will be ideal but do you have the money for down payment, closing costs and reserves for the unexpected. if you do then go for 4 fam. 

If an unexpected repair arises you may be in a tough situation.

If a couple of things break, you have to have an electrician look at something, a plumber look at something, or you have an unexpected repair, or a few months of not having a tenant, you'll be strained financially.

What can I do to prevent my self from unforeseen surprises?

I didn't know they send state inspectors to come to check your business out and I got one come by for a surprise visit.

Once you get started with repairs expect some surprises.