Should I be looking at other types of loans to be more attractive to sellers and refinancing later on down the line? 

What customer service programs do you have in place?

We want to build a custom home and have been exploring different options.

Yes, it is true that when driving for dollars your goal is to find properties with deferred maintenance, create a list in a CRM (customer relationship manager) tool, and contact these sellers with the intention of signing a purchase agreement and assigning that contract to a buyer.

A little secret about contractors: good ones screen their potential customers just like a wise real estate investor would wish to screen their potential tennats.first things first I wouldn't tell any contractors that your an investor and that you have a ton of work you can throw their way.

Also built a custom walk-in closet to it.

If you are willing to collect a few items and share those here on BP, you will attract some of the brightest minds in the space to assist you. 

While long terms such as 30 years are common for institutional paper, they are less common in seller financing and less attractive to note buyers.

Fantastic job at presenting a "normal" house in a very attractive way, with paint, lighting, decorations, and REALLY good photos.  

Be sure to evaluate whether it's an attractive lot.