100% financing is possible but not practical. Hard money lenders that offer it can do 100% LTC and 70% LTV with a higher interest rate and more points than other lenders. You get looped in, thinking they will fund 100% of the deal. Then they get the appraisal done, and the ARV looks too low, so they have to cut leverage to the 70% LTV loan amount.
An example of this would be:
Purchase a deal for $130k, needs $30k rehab, $200k ARV. 100% LTC is $160k, but 70% LTV is $140k, meaning the loan amount would be $140k, even though they "offer" 100% financing. You would go into this deal thinking they will hand you $160k, and then after two weeks, when the appraisal comes back, you have to bring $20k to the table to close.
To make the numbers work on that deal and get 100% financing, you would need to reduce your reno budget by $20k. These deals are very hard to come by, and even when you do think you see one, the appraisal comes in lower than expected, making you cut leverage.