BUYER beware - especially in January.
While delving into the transfer market is always a gamble, history shows shopping in the mid- season window can be particularly risky.
Neil Lennon will be all-too-aware of this as he "puts the pedal to the mettle" on the signings he is attempting to drive home this month.
The pursuit of Stefan Johansen is no whim, the tall Norwegian midfielder having been on his shopping list for several months.
The 23-year-old was preceded through the door at Parkhead by Holmbert Fridjonsson, the Icelandic striker having agreed to begin his Celtic career when the registration window re-opened as long ago as late November.
Their scouting represents the care and attention which must be taken if you elect to do your business at this time of year.
But as the 31-day opportunity to wheel and deal reaches the halfway stage, the pressure to get over the line with negotiations which have been ambling along increases significantly.
Celtic have put themselves in something of a vulnerable position, in terms of demands, having declared their intent to treat the January window as their main business opportunity for this year.
Their logic is simple: With the Champions League qualifiers kicking off on July 15, they believe it would be hugely beneficial to get new recruits in now and allow them six months to settle before the most important series of games the club will play next season begin.
Last summer, they attempted to go early, securing Amido Balde and Virgil van Dijk within days of the window opening.
But while the vast majority of clubs are geared up to sell and buy in the summer window, not many are looking to get involved early.
Switching the emphasis to January goes against all Lennon and Peter Lawwell know about the business of buying and selling. They are in accord that it is the more difficult window in which to trade.
On the whole, clubs who are prepared to allow players to move now tend to do so because these are the guys deemed surplus to requirements.
They may also be players running down their contract and who would be allowed to walk for free the following summer.
In an ideal world, Celtic could secure them on a pre-contract agreement and save a transfer fee.
The exception to all of the above are the clubs who operate in calendar seasons, like the Scandinavians. They treat the January window as their opportunity to revamp their squad ahead of the campaign which will begin again in March.
So it is perhaps no surprise Celtic's first two bits of business involve a player from Fram Reykjavik in Iceland and one from Stromsgodset in Norway.
It will be interesting to see if this becomes a pattern, though Lennon has cast his net far and wide, admitting he has a dozen targets.
Some will already have escaped, either through being unwilling to move to Scotland, or because their transfer fee or wage demands are too great, or because their clubs are not prepared to deal at this time.
As Celtic home in on those who remain on their list - with a goalscorer still the priority -they will have to tread warily.
Evidence of January signings who have failed to deliver is all too easy to find.
Sure, Kris Commons can be held up as a tremendous example of a player who can be bought in this window, and who can bring an instant return.
The man who cost £300,000 from Derby County three years ago this month, scored on his debut the following day, and added another 14 goals before his first season was over.
Mikael Lustig was another January signing who bucked the trend, though he took several months of 2012 to find his stride after struggling with injuries brought with him from Rosenborg, where he had just completed the Norwegian season.
Against those two mid-season hits, there has been a litany of men who failed to fire, some whose stay was so unremarkable or fleeting that most fans even forget - perhaps intentionally - they were ever here.
Without wishing to revive any unhappy memories, how about Rami Gershon?
He came in this time last year, along with Tom Rogic, who is still very much a work in progress after making just 14 appearances for the club.
Twelve months earlier, Rabiu Ibrahim and Pawel Brozek were mid-season arrivals whose stay was short but not so sweet.
Then there have been the marquee January arrivals.
Freddie Ljungberg jetted in amid of flurry of headlines from Chicago Fire three years ago.
But unlike Commons, who was signed a few weeks later, the Swedish superstar failed to make any kind of impression.
Of course, this January judder is not a phenomenon which has only afflicted Lennon's time in charge.
In Gordon Strachan's first season as boss, Roy Keane breezed through from January to May, his debut coming in the humiliating Scottish Cup defeat to Clyde.
The former Manchester United captain did enjoy happier days in the Hoops, including one memorable Old Firm game which allowed him to show what all the fuss surrounding him was about.
But it was a fleeting glimpse from a man whose body clock was ticking and who never became a regular in Strachan's side.
Keane - having realised his ambition to finish his career having played for Celtic, helping them to a league and Scottish Cup double - was soon gone.
His namesake, Robbie, had also been a January signing. In fact, he arrived at Parkhead to put pen to paper so late that, technically, he could have been deemed a February signing.
However, within 24 hours, the belief the man with the pistol-Pete goal celebration was going to fire the Hoops to the league title was shot to pieces as he could not prevent them losing in his debut game against Kilmarnock.
Tony Mowbray was the manager that season, 2009-10, and, in the one mid-term window overseen by him, ill-judged signing was taken to a new level.
Along with £65,000-per-week striker Keane, Mogga madness saw the club recruit Morten Rasmussen plus Jos Hooiveld from Scandinavia for a combined fee of £3million.
At least the Hoops managed to recoup £1m of their outlay when they eventually sold Hooiveld to Southampton.
That was getting off lightly compared to Edson Braafheid, who Mowbray brought in on loan from Bayern Munich for a reputed weekly wage of £40,000.
Though the full-back did go on to play for Holland in the World Cup final that summer, by then he had been blown out of Parkhead on a wave of disappointing and seemingly-disinterested performances.
So, the message is clear. If you feel January is the must-buy month, check, then double check the goods you are about to purchase.