I wanted to keep my budget to no more than $120000.

Yes, if it fits in our budget.

Given your estimated ARV I would budget $132,880 as net after selling. 

I budget $1,000 per year for maintenance and $.67 per square foot for capital reserve on average for a single family. 

With any good model, you should develop at least 3 scenarios: projected or budgeted, best case and worst case. 

Not saying you're wrong, just that you might want to verify your numbers and do some reference checks on the builders (ensure they don't have a habit of over-running budgets).-  The $60-65/sf that we're building in Atlanta is for mid-grade finishes. 

Since I don't have that kind of cash sitting around, I would need private or hard money loan to finance the purchase & rehab costs.If I budget $25K in points/financing for 4 months, a 5% Realtor commission to sell the house and other incidental costs, my total expected costs would be around $600K, leaving $25-50,000 profit depending on final sale price. 

I usually budget my maintenance and capital expenses higher and would probably estimate about an 8% cap on the property. 

It might also mean 80% of the rehab budget.  

Best budget underlayment for hand scraped 8mm laminate wood flooring.