Inconsistent income and hectic working hours or lack of them.

There's never any one thing. What I find frustrating can depend on a specific transaction and who's involved in it. I will admit I do hate this attitude that we need to be available to everyone within 10 seconds or less.

What they said! In my case, I am often frustrated by other people's incompetence, laziness, or indifference. I end up taking on more work than I feel I should just to make the deal close. I should get better at letting my clients know about all the extra, behind-the-scenes stuff I do, but I don't want to badmouth the other transaction participants.

Watching Sellers reject good offers.

Watching Buyers fail to pull the trigger when we find the perfect house.

Having to be a member of NAR.

Other agents not doing their job! 

I don't find this business frustrating in the least.  It is my business, run by me, the way I choose to run a business.  If I'm frustrated, I'm doing something wrong, for me!

Not being able to rely on or predict the behavior of others . 

The arguing back & forth over stupid inspection issues. Buyers are getting outrageous which means we are now scraping the bottom of the barrel.

Rich Gaasenbeek Having to work with people. Just kidding! Working with other agents who operate on their own time clock when it comes to answering telephone calls or responding to time lines in a contract.

People (not all)....they don't always tell the truth and some don't care if they waste your time or not. Yes that is very frustrating.

Dishonest clients. They do not tell you their true intentions.

For me the most difficult part is dealing with agents that don't know how to do their job and end up leaning on me to do it for them in order to get the transaction closed.

figuring out who are ready to buy and who are not. therefore i tend to caution on the side they are not ready.. i may miss some opportunities, but i have moved to the camp, when they are ready they will act..

All the comments so far are on point! The most frustrating thing I have run into is other agents, not all of them and not even most of them, but like with any job dealing with people who are not as dedicated as you can be quite frustrating!!!!

That the public does not truly understand what we do.

other Real Estate Agents who make up their own rules as they go!

Dealing with people who don't know what they're doing.

witnessing other agents providing incorrect information.... 

Which CRM is easy to use and cost right?

What day is today, Hmm Wednesday - let me check my calendar and get back to you on this...

People who fail to communicate!

The lack of professionalism when working with some other agents.

The long hours and dealing with some of the agents.

Robin Rogers nailed this one!!!

Professionals who aren't professional. 

Buyers who aren't really buying.

Sellers who aren't really selling.

Other agents, loan officers, clients, etc., who do not return phone calls or emails. 

The ultimate most frustrating is working weeks and months with a client and they meet another agent at an Open House and they promise them that they will get the house if they use them! I think there are some unethical agents that went to the same school! Lame O School of No Morals. 

Rich Gaasenbeek - nothing! They are just people in our community.

Basically I love my job, but I hate it when people don't respect my time. 

I don't get frustrated very often, and when I do it usually has something to do with some new app that I can't figure out.

I actually don't find my business frustrating. I have a wonderful full time  Administrative assistant who eases my work load..makes all the difference in the world.

People that call at 9:00 PM and have to see this house right now!

Wow, Lots of great answers. I think for me it's buyers that find the house but scared to make the move. 

The other agents.

Right now it is the shortage of homes to sell.

Dealing with agents that don'r put their clients first and are missing in action much of the time after an offer is acepted

Buyers who do not know what they want.

Being a newbie, I'm sure my answer will not be the same a few years down the road, as it is today, Rich Gaasenbeek.  For me, the most frustrating situations involve new clients that are difficult, want everything, complain about the cost, and are unrealistic in their expectations and pricing - though they are not quite in the Bully category.  

No frustration...human nature when known correctly preps U for anything

The most frustrating factor in real estate and in business is government control, over regulation which seems to get worse every year.

That people expect you to be at their beck and call.   They think they can call you and you'll drop everything to accommodate them... as if you've been waiting your whole career for this one moment to serve them.  LOL

And, what Annette Lawrence , Palm Harbor, FL 727-420-4041 said about being put on the front page of Google.  It annoyed me to no end when I'd get those messages.  I already had the top 7 spots for market, achieved organically through blogging.

Really having a good time and staying in zen mode. That is not what is frustrating, it is the way I feel. However, builder delays can sometime raise my blood pressure just a tad.

"You're all the same. Don't show me all your charts and reports, just tell me what it's going to cost!"

That is frustrating, knowing past experience has created such opinion, but it is not the end of the world.

I take up the conversation  at the cost of not hiring me.

ON the more practical side, frustration follows hearing, "I can put you on page one of Google" for the 6th time today.