I'm an agent and investor who has been growing my sales business for 6 years and my investment portfolio for 5 years. Having a real estate license has been a huge benefit because it has allowed me to grow both my businesses by doing the same work. Here are a break down for the reasons that you should or shouldn't get a license.
Perceived pros:
1) Access to MLS Data: The realtor MLS will have access to more information than Zillow, that will be beneficial for an investor (Primarily the Rent Roll)
2) Save on commissions: The commission would be paid directly to you, so you would get a 3% discount on all properties you purchase
3) Networking: Being licensed helps you build relationships with agents, brokers, and investors to help find deals that may be worth pursuing.
4) Off market listings: Since you will be lead generating for listings to sell as a real estate agent, every deal you come across is a potential property to purchase.
5) Additional income: You can earn commissions by representing other buyers and sellers to purchase properties that you decide to pass on.
Cons:
1) Time & Cost: Licensing requires education, exams, fees, and ongoing continuing education.
2) Almost every benefit I mentioned above can be done without a real estate license, so there is it's a lot of money and time for no benefit.
Yes, the biggest con to getting a real estate for an investor is that it doesn't help at all. I put perceived pros, because you could do the most of the pros of having a license without getting one, as listed below.
Why the pros aren't really pros:
1) Reach out to your number one agent that you've been growing a relationship with. If that doesn't work, reach out to the listing agent directly to get the missing information.
2) After the first one or two deals, you'll be getting more than a 3% discount because you should be getting better at finding/negotiating deals, on and off market. Even as an agent, if another agent brings me a deal 10% or more below market value, I want to pay him 3% (Even if it is out of my own pocket) so that he continues to bring me deals. Some people will say that agents buy all of the good deals, so there aren't any deals left for the investors. Statistically, agents don't own investment properties, and if they do, it's just one or two units. This means, for all of the great deals they find, the only way they can make money on the deals, is to get a commission form selling it.
3) You can network with agents and investors, without having a license. Find the agents that do a lot of multifamily investing in your market and call them to schedule lunch or coffee. Network with them and make sure they know that if they bring you a deal that goes to closing you will pay them their commission of 3%, even if the seller doesn't pay it. You don't need a license to network with people.
4) All the lead generating that you would be doing as an agent can be done as an investor. Door knocking, cold calling, direct mail marketing, etc. This is the work you would be doing as an agent to find leads to buy or sell. You can, and should, be doing the exact same thing as an investor. Sadly, just because you have a license, doesn't mean off market deals fall into your lap.
5) This is the only real benefit to having a license. Since you will be lead generating to find off market deals and buyers, if you find a good deal that isn't perfect for you, you can sell it to someone else and get a commission. Although, if you are doing this, you are becoming an agent. An being an agent isn't easy, 70% fail in the first year.
All of that to say, the only reason you should get a license is to sell real estate. If you wish to be a real estate agent, get a license. If not, there is no real benefit and it will cost you more time and money than it is worth.