why not knock on the doors in the neighborhoods that you are doing tear downs and remodels on? It sounds like you already know how to market/find properties for your construction work - leverage that same skillset to find flips.
You have an advantage over most beginning investors in that you know more accurately what the rehab costs will be for a certain project. That piece is often underestimated by many.
For the other key numbers:
The structure is Maximum Allowable Offer (MAO) = ARV - Holding Costs - Rehab - Closing Costs - Profit
ARV (after repair value based on recent sales within a 1 mile radius. Go conservative )
- Holding Costs (loan payment, utilities, insurance, etc)
- Rehab Costs (you will have a good handle on this)
- Closing Costs (you will pay closing costs on both purchase and sale of home)
- Profit (minimum you would want to take on the risk. This is the most "flexible" of all the items)
There are plenty of resources here to help you on your journey!