The engineer can help with this estimate, but local contractors are the top source for getting this info. 

If that's the case and you aren't viewing more properties in person than you are making spreadsheets on, you are destined for analysis paralysis.Spreadsheets can only tell you estimations based on numbers given to you online or by a real estate agent whose job is to sell the property.

A major challenge for me (and, I understand, for many new investors) is estimating the price of renos needed, which of course makes it difficult to know what's a reasonable price to offer!

Are you getting estimates in DD to decide?

We will evaluate their portfolio, estimating the purchase price and current value of every deal they've done from the beginning of time.

Additionally, I'm interested in understanding typical STR fees to help estimate cash flow.If anyone is willing to share their experiences or offer advice, I would greatly appreciate it.

Run an estimate for $175k refinance cash out on a 30 year and you may still be able to make 250 cash flow and have 100k to reinvest to buy more real estate.

Let’s break it down with your example and explore the financing options.Max Leverage (Using a Lender for 90% Purchase and 100% Rehab):Purchase Loan: 90% of $80,000 = $72,000Rehab Loan: 100% of $25,000 = $25,000Total Loan Amount: $97,000Your Cash Investment:Down Payment: 10% of $80,000 = $8,000Closing Costs and Fees: Estimate around 3-5% of the purchase price = $2,400 - $4,000Holding Costs: Property taxes, insurance, utilities, and interest during rehab (estimate $1,000 - $3,000)Contingency Fund: 10-15% of rehab costs = $2,500 - $3,750Total Cash Needed: $8,000 (down payment) + $2,400 - $4,000 (closing costs) + $1,000 - $3,000 (holding costs) + $2,500 - $3,750 (contingency) = $13,900 - $18,750Moderate Leverage (Using a Lender for 90% Purchase and 0% Rehab):Purchase Loan: 90% of $80,000 = $72,000Your Cash Investment:Down Payment: 10% of $80,000 = $8,000Rehab Costs: $25,000Closing Costs and Fees: Estimate around 3-5% of the purchase price = $2,400 - $4,000Holding Costs: Property taxes, insurance, utilities, and interest during rehab (estimate $1,000 - $3,000)Contingency Fund: 10-15% of rehab costs = $2,500 - $3,750Higher Equity (Using a Lender for Less than 90% Purchase):If you decide to put more equity into the deal by using less leverage, you will need more cash upfront, but your loan amount and, subsequently, your interest payments will be lower.

Most have never done a single deal, have no money to close on the property if needed and have no clue how to estimate fair market value or ARV or sell a property.  

. - Expect rehab costs to exceed initial estimates (maybe double)!