Anything over 5+ units in a building is generally considered commercial residential at that point. This means that the lender/bank is going appraise and provide a loan based on the NOI of the property and not necessary the stated "value" of the asset from comps and so forth.
A 15 unit building with 50% vacancy and below market rents will be cheaper than the exact same building that has a 15% vacancy and has the rents at market rate.
You totally could jump right into bigger deals but you must keep this in mind. It depends on the strategy you want to deploy. However you could raise capital from investors for the downpayment on a building that has the value add opportunity. You then stabilize the asset. Do necessary repairs/updates. Fill vacancies. Increase rents to market rate. THEN approach a the lender and refinance your loan to cash out the added equity to recoup the initial investments and ideally some cash for you to repeat this process.
It's worth noting, the bigger the deal you take on at first you will be going through trial by fire. The caliber of investors, contractors, lenders, agents, and red tape you will work with will be much higher at that level. If you don't have the skillset to run the play then these people WILL run you over and take your lunch. It's very possible you just have to be self-aware to what your strengths and weaknesses are as you go through the process.
Also, as you take on bigger deals the network you use to execute the deal have less patience for you. They assume if you're swimming in that pond - that you do indeed know how to swim. They will be less tolerant of ignorance, errors made, and will not care if you don't know what you're doing.