We have also tried Proper, which seemed so promising, but they don't cover our zip code. 

According to the Texas Business Commerce Code (TBCC) Section 1.201(b)(27), Legislators defined Texas series LLC as a legal “person.”

However, I want to be able to change the lock box code or make it so that I can lock it.

Financial Transparency:Managing the budget yourself allows for greater transparency in costs, helping you to identify where money is being spent and find opportunities for savings.It's important to consider the potential downsides, such as the significant time commitment, the need for substantial construction knowledge and experience, the risk of costly mistakes, and the responsibility for managing permits, inspections, and compliance with building codes.

I wouldn't do a lot of architectural plan work until you know what complies with city code, especially if that particular parcel may have any limits/constraints.

It contains more detailed information on investing insights, analytics, and, particularly, investing in Las Vegas.Before proceeding, note that the charts only include properties that fit the following criteria unless stated otherwise.Type: Single-familyConfiguration: 1,000 SF to 3,000 SF, 2+ bedrooms, 2+ baths, 2+ garages, minimum lot size is 3,000 SF, one or two stories.Price range: $320,000 to $475,000Location: All zip codes marked in green below have one or more of our client’s investment properties (click to enlarge).Overall Las Vegas Real Estate Market InventoryThe chart below, provided by the MLS, includes all property types and price ranges.The inventory level continued its downward trajectory, significantly lower YoY.Rental Market TrendsThe charts below are only relevant to the property profile that we target.Rentals - Median $/SF by MonthRents continued the up trend as expected.

Have a developer working on designs at the moment to see if even possible with city codes.

Any recommended zip codes ?

you have to look at your building code and talk to GCs who have done it.

That would be against code of course.