You need to use onClientRender to draw it. 
addEventHandler ( "onClientRender", root, 
    function ( ) 
        local x1,y1,z1 = getElementPosition ( marker ) 
        local x2,y2,z2 = getElementPosition ( marker1 ) 
        local x3,y3,z3 = getElementPosition ( marker2 ) 
        local screenWidth, screenHeight = guiGetScreenSize ( ) 
  
        local x1_, y1_, dis = getScreenFromWorldPosition( x1, y1, z1 ) 
        local x2_, y2_, dis = getScreenFromWorldPosition( x2, y2, z2 ) 
        local x3_, y3_, dis = getScreenFromWorldPosition( x3, y3, z3 ) 
  
        dxDrawText("police job", x1_ + 2, y1_ + 2,screenWidth,screenHeight, tocolor ( 0, 0, 0, 255 ), 1, "pricedown" ) 
        dxDrawText("police job", x2_ + 2, y2_ + 2,screenWidth,screenHeight, tocolor ( 0, 0, 0, 255 ), 1, "pricedown" ) 
        dxDrawText("police job", x3_ + 2, y3_ + 2,screenWidth,screenHeight, tocolor ( 0, 0, 0, 255 ), 1, "pricedown" ) 
    end 
)