Relationships with agents? You are looking for an agent to refer off market properties?
Just my opinion as a broker investor for many years. Most agents are living from one settlement to another, loyalty is mostly to their commission split and to their already long established clients customers and to their spouse looking for a pay-check!
I think what you want is some inside off market deals with a ton of equity, agents with the ability to ascertain equity and owner motivation have a long list of folks who'll make offers to hijack a profit. Or, just grab it for themselves.
You don't "find" relationships, you need to build them! That takes time.
Lets start with you! What do you bring to the relationship as an investor? You have cash? A credit line? what is your criteria to make an offer? Any of these; must have a ton of equity, seller needs to financing, got to be purchased below market value, must be approved by lenders appraisers or other gate keepers... your wife, your partner, your cpa or mother? How have you figured your profit potential (long term, immediate cash, assignment or JV, or hold and collect rent?
Agents don't want to nurse or education anyone, they are too busy trying to get listings and sell what they have. - THEY ARE all about how much commission is in the deal, what's the split and how fast can we get to settlement!
Your best agent is the one who represents you on a fiduciary basis, that is a BUYERS AGENT. You need an agreement with the Buyers Agent, pay a commission on unlisted properties, you should treat them with respect and be clear on what you want and where you went it, share with the agent the amount of cash you have on hand or can get with in 24 hours, and before you look at a property, look at the numbers first; what's the liens, condition, how long on the market, comparable sales potential equity in the deal. Don't use your agent like a new toy, be ready to make serious offers.
One of the best ways to become market savvy is to look st 50 houses before making even one offer, keep a journal, price per SF, note comments from sellers and agents, copies of listings and all supporting information, do this and you will know the market as well or better than agents..... do this and the only relationship you'll need is with yourself and the market.
Cheers, just my opinion --- Charles