Even more incredible (and extremely sad), those with $40,000 saved are willing to spend it all (usually eagerly) on a mentorship program in which they have done no research and demanded no proof that the program has been successful, other than read some hand picked testimonials from the guru's students.  

Should I put a percentage of my rental income aside or should I pick a set amount?

Just make sure you pick a house that isnt going to need a new roof, updated eletrical, plumbing, ect.  

So the city will pick up garbage for Multi-family units.

Since the markets have picked up, everyone believes they can flip real estate like you see on HGTV and the market is getting flooded with fix and flippers.

I would first pick an area you want to invest, study it, and then find a commercial broker to develop a relationship with to get more information on properties within that area.

Read books on investing in real estate, listen to the podcasts, attend webinars and stay active on the forums while connecting with other investors in your area and pick a niche.

This is the quickest and best way to get started with the least cost.First pick a neighborhood that you are either in or close to.

I also am continuing to pick up rentals to build my long-term portfolio.

I pick it up from there on the sell side.