First thought is that this depends on your market.  

@Louis Mannikko  if your 401k is a solo 401k that you control.. you may want to look at investing NOtes or with a HML.. this is a very good use for those funds.on the fix and flip you may want to consider partnering up.. just make sure whoever you partner with is vetted thourougly.. plenty of " my idea and your Money guys out there" you can go on amazon or E bay.Look for any of the guru's written material and videos you can get those for next to nothing. look through them there are usually nuggets in each one that you can use.you can also spend untold hours on BP asking questions and reading and listening to pod casts etc.. of course this is free and just depends on if you have the time for that.

That said depending upon where your income is already you may have issues.

HELOC can free up the additional 10-15%, but comes with a price (fees, higher rate, higher risk).It may take a while to save another down payment on annual positive cash flow from 1 property, depending on your numbers.  

In that case, the tenant given notice to move out needs to be paid relocation fees depending on a formula of how long they've lived in the unit, how many people, etc.  

Depending on the policies of the real estate company they may take a flat fee or a % of transaction (remember there is only one side your agent is representing so you should be able to secure representation for 3% or less of purchase price), negotiate that up front.

@Truong Tran It all depends on how the agreement is written.

Depending on the property, your partner's investment of time and money, exit strategies, etc., you will have to give up 50% to 75% of the profits as the price of your education...but don't forget you're still getting paid for learning. 

It depends on what you are looking to do, fix & flip, buy & hold or wholesale.

Bigger Pockets should add auto hints that recognize the names so your not dependent on the "@".