All very good suggestions ... I have been in the same stage of researching for better prices on various building materials
1. Building supplies auctions - these usually don't seem to have good info on the websites and you have to go to them physically .
2. Clearances and sales in all the stores such as Menards , homedepot , lowes . Ofcourse online stores such as wayfair , houzz and others also might have good deals
3. OOPs sections in the big box stores : These might not always be advertised online, but especially things such as paint ,tiles ...might have pretty good deals
4. Appliances : Sears outlet seems to be the one beating all the prices .
5. Habitat for humaity , restore and these go by different names in different places - And also sometimes you would get new items here
6. Floor model pieces : there are some sites where they sell floor model
7. Facebook market place / craigslist : Hit and miss and more time taking
8. Specialty stores : Again specialty store doesn't mean better price , so have to pretty much validate the prices and quality like anywhere else . some online specialty stores , who have the worlds horrible websites have such good deals .
Not directly material related :
1. Looking for better labor prices : You will hear "you get what you pay for" mentioned everywhere . But the reality is sometimes you get , sometimes you won't . Whether you hire the highest bidder or the lowest bidder , you will need to have a process in place to identify and handle this situation .
2. In some cases investing in better tools helps , especially the ones which would cut down your learning curve . But the challenge here is to know what is the right way to do certain things and that is not always easy .
One caution :
1. If you are not a professional flipper with many projects : One important suggestion is that sometimes sites such as buildersdirect - have items marked significantly higher than lowes/homedepot . So if you have time , compare costs and just don't assume that as you got a good deal on X , you might get a good deal on Y