HELOC vs. Cash??

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I own a rental with $124,000 in equity. ($260,000 value / $137,000 still owed at 4.00%). It brings in $1,800/month. My mortgage is $1,050/month.       I would like to invest in another long term rental property. I have $50,000 in savings (not retirement). Should I use cash for a down payment/ closing costs or a HELOC? If I could cover the HELOC payment with the cashflow from my current property, it seems like a no brainer. Is there something I'm not seeing?