@Simon Battistella, Bonjour! I'm 24 as well slowly building up my portfolio. I was also born in France so it is nice to see a fellow France native on Biggerpockets. I currently have 5 properties in Philadelphia. Where are you buying, University City by Drexel?
When you say you want "full" financing...what do you mean? 100% financing? In some instances, you may be able to obtain 100% financing from hard money lenders IF your purchase and rehab costs are 65% of the ARV (after repair value)...keep in mind that hard money loans are short term loans with high interest rates and origination points. Since your goal is to buy and hold you would have to refinance into a longer term loan once the rehab is complete and the property is stabilized with renters.
If by "full" financing you meant was not personally guarantee your loans- in most cases you will not be able to do this anymore. I have seen some lenders do this, but this comes at much higher rates and terms that it is generally not really worth it.
I think that 6 properties is a good start, each bank will look at your portfolio on a case by case basis including your personal financial situation. I.e. if you have any other debts, cash in the bank, etc
Feel free to DM me with any questions