Should I take a cheap river card or keep betting my draw?

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I don't know anything about the opponent. It's the min lead on the turn that has me thinking. In my experience a min lead on a turn is a bad player playing a big hand and is now desperate for me to raise him or that the turn has just brought him some kind of draw. So, if I'm half expecting to get check-raised here should I take the cheap card? Or should I just act like the min lead didn't happen and make my standard bet here?

Full Tilt Poker, $0.25/$0.50 NL Hold'em Cash Game, 4 Players
LeggoPoker Hand History Converter

UTG: $76.80
Hero (BTN): $50
SB: $50
BB: $98

Pre-Flop: Q[img]/images/graemlins/heart.gif[/img] A[img]/images/graemlins/heart.gif[/img] dealt to Hero (BTN)
BB calls $0.50, UTG folds, <font color="red">Hero raises to $2.50</font>, SB folds, BB calls $2

Flop: ($5.50) K[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/club.gif[/img] 2[img]/images/graemlins/heart.gif[/img] (2 Players)
BB checks, <font color="red">Hero bets $4</font>, BB calls $4

Turn: ($13.50) 9[img]/images/graemlins/club.gif[/img] (2 Players)
<font color="red">BB bets $0.50</font>, <font color="red">Hero raises to $8</font>, BB calls $7.50

River: ($29.50) 5[img]/images/graemlins/club.gif[/img] (2 Players)
BB checks, Hero checks

Results: $29.50 Pot ($1.45 Rake)
Hero showed Q[img]/images/graemlins/heart.gif[/img] A[img]/images/graemlins/heart.gif[/img] (Ace King high) and LOST (-$14.50 NET)
BB showed 5[img]/images/graemlins/heart.gif[/img] 6[img]/images/graemlins/heart.gif[/img] (a pair of Fives) and WON $28.05 (+$13.55 NET)

Also, if checked to on this turn, how often are people taking a free card versus betting? I always just bet here as standard but is this correct?