Down here at the fun end, the cost structure is different. You're primary costs will be:
- Fees
- Actual bid amount
- Taxes, DMV registration, insurance, etc.
- Parts
- Delivery
Of the items above, the Actual bid amount is the easiest to estimate. Just pick a number you will not go over. Click each of these links to see more details on how to configure the Copart and IAA interfaces for searching within your budget.
Variable costs can include tools, disposables like oil, depending on what you have in your shop.
Here's an actual breakdown from a sale:
From a 
2013 Infiniti G37 purchased in June 2022:
- Sale Price: $1,350
- Buyer Fee: $435
- Virtual Bid Fee: $69
- Gate Fee: $79
- Environmental Fee: $10
- Delivery: $85
Total out the door: $2,018 - about 50% more than the winning bid amount due to fees.
And here's another example from a 
2001 Porsche Boxster purchased in September 2022:
- Sale Price: $2,475
- Fees: $720
Total out the door: $3,195 - about 30% on top of the winning bid in fees. The vehicle was later sold to Copart/cashforcars for $1,300, representing a loss of $1,895 plus repair costs.
The lesser known fees
Membership fees - certain auction houses and brokers require annual membership fees. In addition, they require upgrades to membership, deposits or other fees to increase your 'buying power'. Think of these like gotchas from the credit card companies. As long as you remember to request the refund of your deposit, and factor in membership fees for your budget, you'll be fine.
Documentation fees - having the documents mailed via fedex can add to your cost.
Insurance - you'll need to add the vehicle to your insurance policy.
Title transfer fees - you'll need to pay the DMV to transfer the title.
Inspection and Registration fees - this can easily add hundres of dollars to your overall cost, and that's if it can pass the inspection without a second try.
Delivery and Storage - most of the time the delivery truck driver can put it right in your garage. If not, you'll need a plan for getting it to your house, or pay for storage.
Tools - you may need to buy or rent specialized tools to perform the fixes.