Ordering of finding a contractor vs making offers?

[Reece Teramoto]

I've read David's great book on long distance real estate investing, but there was a catch-22 that I couldn't quite figure out. It comes down to finding a contractor vs making an offer on a property.

Here are two of takeaways from David's book:

1. To find a good contractor, start off with a couple of them, have them each submit an itemized list of rehab line items for your property
2. A good rule-of-thumb for analyzing properties (with the BRRRR method) is the following formula: (Purchase Price + Rehab Costs) * 0.75 < ARV

How does one go about doing both? It seems that in order to make an offer on a property, you'll already need to know the rehab costs, meaning you've already settled on a contractor. In order to have multiple contractors submit an itemized rehab list, you'll already need to have secured the property. If either of these statements are incorrect, please let me know. 

So for someone just starting off with long distance real estate investing, it seems like the best option would be to find a property that seems like it could be BRRRR'd, have multiple contractors do a walk-through and give you an itemized rehab list, then based on the their costs, figure out what can be offered for the property for the numbers to make sense. However, if you have a list of contractors, it seems like this process might take a while (or maybe you can have all contractors visit on the same day and submit itemized bids--please let me know if this has been the case for you!).

After all contractors get back to you with their bids, I envision one of the following scenarios happening:

1. It's taken too long and the seller of the property has chosen another offer. 
2. You've determined that the rehab costs will be too high and it doesn't make sense to purchase this property unless you make a much lower offer that might not be accepted.

In both of those scenarios, would I would risk severing ties since in both of the scenarios, I'd have to find another property and repeat the process with all contractors? Or are contractors used to putting in bids and then having the investor not close on the property, but then asking them to submit a bid for another property? 

I mainly want to make sure I can find a good contractor but still be respectful of everyone's time. If anyone could provide guidance on the ordering of how one can go about finding a contractor but also putting an offer on a property, please let me know! Any advice would be greatly appreciated!