I'm not comfortable with them, especially for the first 4 items.Would you kindly explain to me for each of them?

BiggerPockets is full of resources designed to help you along your journey, whether you are just getting started or a seasoned investor.

While I haven't done new construction as an investor, I've been involved with them on the design and construction side. $15-$20,000 seems like a very small profit on a $500,000 house.

Lending terms will be important here.I'd say the biggest challenge thus far is making sure I feel comfortable managing this remotely, as it's located about ~150 miles east of Dallas. 

Now to provide extra comfort and convenience to our buyers (who are mostly out of state) we agree to help them out by getting them set up with local property management that we work with closely as well as assisting management market the property for rent to place tenants.

Just make sure to research your local rental market and get comfortable estimating rehab costs.It’s a smart plan, and you’re off to a great start.

If I don't feel comfortable I also give folks a chance to get a cosigners.

A primary residence will most often provide more favorable loan terms so if you are willing to wait one year while you living in your new property and are comfortable with renting out your primary residence to a tenant, then getting something such as an FHA loan is a good strategy to minimize your upfront costs and hopefully get better loan terms.

It is also comfort level with the B2C relationships.  

The property manager can make or break you, it has to be a PM that is working in that space and is comfortable there.I agree with earlier comments to look in the front and back yards to see how many old cars, abandoned junk, or treasures that aren't treasures are piling up.