Even a single family builds can vary significantly based on site conditions and required structure/design.

Beyond the bedrock issue, soil conditions can be costly if the property has problematic soils such as too much silt, deep topsoil, or extensive wetlands.You'll also want to know what ordinances are going to affect your budget - things like tap fees, tree ordinances, storm water retention policies, etc.Bottom line is that you have to investigate ordinances, off-site conditions, and on-site conditions before you can even begin to budget your development.

We are asking the current tenants to leave as the property is not in optimal condition we like to have our rentals and we would like to fix it up to increase value and rents.

This demographic is projected to keep increasing over time, so I would do whatever you can to hold onto this property (ie cash flow well).Furnishing 700 sqft with PB or West Elm (you and my wife would get along great, Bonnie) won't be price-prohibitive and well worth the cost.

My previous tenant left the yard in a poor condition before moving out.

I have been in Milwaukee WI for quite a while as investing in my backyard in NY is cost prohibitive. good luck on your journey!!!! 

@Polat CaglayanI've never seen a formula but here is a general rule of thumb for multifamily:The class of an apartment refers to the quality of the building, which can be determined by a number of factors, including age, location, and condition: Class A: These are the highest quality apartments, typically built within the last 15 years.

A "lake house" might be in a residential zoned area where a commercial use would be prohibited or at least require a variance (approval) to make an exception.

I’ve found a duplex that seems to be in good condition, with both units currently rented out.

She did move in two cats during her tenancy (with my permission after the fact), and the house was left in fairly good condition when she moved out:Most holes were patched (though some in the basement were missed).It was moderately clean but needed extra cleaning due to cat hair in the carpets.Minor issues included:A missing doorbell.Missing shower hardware.One of the window blinds needed replacement.A truck bed full of items left in the shed that I had to haul away.Since I was in a pinch between Christmas and New Year’s, I hired professional cleaners for a quick turnaround.