I am currently on the AE scheme but am starting to look into moving up to an EIRL or EURL, but some of the horror stories regarding the RSI are concerning to say the least!
Some people say you pay 48% others 'only' 36% cotisations & income tax, and all the simulators return different figures so it's hard to gauge the true cost without paying an accountant/business advisor.
If you're a builder you are not profession liberale! You are an artisan dealing with RSI and profession liberales deal with URSSAF. It is difficult for anyone to say with the vague details you have posted.
Firstly, are you an auto-entrepreneur or under the standard scheme? If you're an AE then no expenses can be claimed. I guess you're not theough as the RSI doesn't work like that for AEs. Under the normal scheme, you'll pay a forfait for the first couple of years and everything's adjusted in the third year. I've had different demands during the first couple of years as they keep changing what they think I should be paying - currently at 6400€ but it'll all get sorted in my third year when it often goes up significantly. Charges sociales are around 46%, here's a simulater for RSI charges sociales. If I remember correctly, you can put expenses against tax but not charges sociales, unfortunately!