Where to start? Architect? Engineer? Both? Recommendations?

Hello Brownstoner community, Long time lurker finally coming out to ask you experts your advice. I’m closing on a property at the end of the month. A 25×100 lot in an R6B zoning area with a legal pre-existing curb, non-landmarked, cut to be exact. 
My intentions for the property is a complete demo of the current building and rebuild of the place for the ground up. This is for personal use, looking to put a 3 family on the lot, with parking. I want to maximize FAR and height (which i believe is 50′ with the 10 foot set back) Also looking to put in an elevator into the building. 
So my question where do i start, do I need both an Engineer and Architect? Are there folks that can do both? Do I just need an architect? just an engineer? What are the differences?
Also would love some recommendations as well. Looking forward to hearing from all of you as I start this journey.