Building new rental property need advice on size of dwelling

[Chad Stubblefield]

My wife and I are partitioning part of our property and we are going to build a single family residence on the new lot to hold and rent. I am looking for advice on the size of house to build. The lot size will be around 4500 square feet (45 x 100) so we have been looking at narrow lot plans. We have narrowed it down to two we like.

The first home is 1252 sqft, it has a double car garage and has 3 bedrooms and 2 baths and is a single story

The second home is 1642 sqft and is 3 bed 2.5 bath, single car garage, and it is a 2 story

We will own the lot free and clear after the partition, and the first home is going to cost about 125k to build, turn key. The second home will cost about 145k. My wife is a residential appraiser and she has comped the first two properties. We feel that the first property will have a market value of 170k and the second property will have a value of about 210k. The thing that gets my attention is the second property is worth about 40k more with only an initial investment of 20k, but I don't want to get to ahead of myself because We are building this as an investment/income property. Based on the research we have done in our market, we believe that the first home will rent for around $1150-1200 a month and the second home will rent for about $1250-1300.

ANY ADVICE IS APPRECIATED. Even If you have a different way of looking at things. I am open to any and all input!

Thanks!