If you close in 45 days with a normal owner-occupied loans, you should be able to make competitive bids. 

Most flippers I know who work that area would want to put it on the market where the competition is likely to fetch more than asking.

Competition isn't real -- if you have a good product and there are customers for that product, you can succeed.You get off market deals by contacting people that are off market and seeing if they would sell. 

Has it gotten increasingly more challenging recently due to the more competitive market?

The best thing about thumbtack is anyone providing you a bid understands there will be competition because that is the nature of the site.Best of luck!

I studied civil/construction engineering in college and I work for a global Arch/Eng. and I've learned to become borderline obsessive when pricing and putting estimates together. 3+ days and I'm still carefully gathering cost information.  

@Stuart GardnerDon't be discouraged, the Boston real estate market has a lot of competition and is a sellers market so there is little supply and prices are high.

To be safe you want to have any non-licensed person you work with sign a disclosure that you are not representing them.In a competitive situation the experience of an agent can make the difference between you buying the home and a competitor getting it.

Many wholesalers are moving to the suburb towns of Nashville in search of less competition (dickson, white's creek, goodlettsville, etc)

All depends on your motivation to own it and what you think your competition (other buyers, if any) will be offering.