How to estimate reno costs

[Mick Murray]

Looking to purchase our first BRRRR. There are multiple distressed properties in the area I want to purchase, but I don't want to wear out my contractor in getting bids in order to calculate ARV to make an offer. I'd like to be able to eyeball and estimate reno costs, make an offer, and then get the reno bids in the option period. But I don't know where to start to estimate reno costs.

Any tools you'd recommend?  Standard multipliers?  Rules of thumb?

Thanks