There isn't a single floor, but here's what the costs actually are so you can build your own number.
On a 100k purchase with hard money or a renovation loan, a lender typically wants 10% to 20% down on the purchase and will fund the rehab in draws, meaning they reimburse you after each stage of work is inspected. So you're out roughly 15k down, plus closing costs of maybe 3k, plus you have to front the first draw of work before you get paid back, call it 8k. Add lantern's holding costs at 7k. That's around 33k before the refinance returns anything, and none of it includes a reserve.
The reserve is the part the 25k articles skip. If your rehab runs 20% over, and a lot do, you need cash to finish. No lender bails you out mid-project. Most experienced operators keep 10 to 15k liquid on a small deal purely for that.
Tools: a spreadsheet genuinely does the job at one deal a year. Paid deal analyzers run roughly $30 to $100 a month, and property management software for a handful of units is often free or under $30 a month. Nobody needs any of it to underwrite their first house.
Insurance is the part specific to this strategy. A standard landlord policy generally won't cover a vacant property under renovation, so you carry a builder's risk or vacant-property policy during the rehab and switch to landlord coverage once a tenant moves in. Tell your agent the property will be unoccupied and under construction, in those words, and get the coverage confirmed in writing.
No license is required to buy and renovate property you own. What varies by state is whether you can do the work yourself or must use a licensed contractor for things like electrical and plumbing, and whether pulling permits as an owner-builder is allowed. Check your state and your city, because they can differ from each other.
