The effect of combined resistors?
Well yes, you can combine in series two 1k resistor in order to make a 2k one. 
However, if you want to draw some current from this new voltage point, you rather use a linear voltage regulator such as 7805 or a LM317 combined with resistor. 

A little tips about resistors in series :

By using two resistors in series, the power is also split equally across both resistor.

The current passing through each resistor is still the same but resistor's value is twice lower, so the dissipated power for each resistor is also divided by two. This can lead you a technical choice in some case of high current or cost restriction.