I estimated his monthly payments are $989.

Or is this your estimated value on it?

We did a decent job estimating our budget, considering it was our first time.

What are some recommendations for getting smart on managing rehabs, working with contractors, and understanding how to estimate costs on a fixer upper?

If all else fails, I would get at least 3 estimates and go with the most reasonable. 

The #1 mistake new wholesalers make is over estimating the price of a property while under estimating the cost of the rehab. 

When you first apply you'll estimate what you think your home is worth and that will be your initial estimated LTV but once your appraisal is completed the true LTV will be calculated.

Investors with the ability and confidence to walk into a property and accurately estimate rehab costs have a huge advantage in this market, but it looks like inspections periods are becoming deal killers – at least in hot markets.Are inspection periods killing deals in your area?

That's how to come up with an offer quickly and easier without making a (bad) estimate of repair costs and multiplying by a percent, etc. 

We are currently looking into construction loans and that are requesting the the estimated value of the property.