Typical new build will have primarily 3 segments for value creation 1.

Since I may have to do them anyway for the next person, I'm OK with doing anything a landlord should typically do.

There are typically no contingencies that I am aware of in a land contractCan you provide an example ?

I typically suggest my clients engage a land development specialist to assist with this process. 

Property tax websites are unreliable, as they are typically only updated around the time tax bills are sent out, which is only once a year in my county.

They are typically state-specific?

I suppose 5% on repairs could be okay but it depends on the condition of the property and the type of tenants you'll have in that area.For management, usually I will put at least 10% in my analysis (especially for a duplex) as any property management company will typically charge a placement fee (usually 1 month rent) when they place a tenant in the unit.

Rob Auction.com typically starts off high but if there are no bids, sometimes they will run a second round at a lower price a few hours later. 

Our county GIS sites also typically provide a photo of the comparable property.   

However, if you are looking to increase monthly cash flow to earn a better return then I would suggest looking for longer amortization (25 years is typical) and possibly 80% LTV.