Significance of the word "wealth" in Jaravagga The Story of the Son of Mahadhana
  
  Neither living the chaste life
  nor gaining wealth in their youth,
  they waste away like old herons
  in a dried-up lake
  depleted of fish.
  
  Neither living the chaste life
  nor gaining wealth in their youth,
  they lie around,
  misfired from the bow,
  sighing over old times.


I imagined "gaining wealth in their youth" would mean spiritual wealth, after all a lot of materially rich old people I know do sigh at old age, because material pleasures are often best enjoyed in youth.

Yet, the back story seems to indicate the Buddha did mean material wealth, which is odd. Granted,  being rich and old is better than poor and old, still, old age to the unwise is great suffering.

Of course, Buddhism doesn't ab initio criticize wealth, or beauty. They are said to accrue as a result of good deeds, and are desirable as long as they don't interfere in bettering one's virtues and mind. 

Still, it's not a perfectly flawless argument to equate pious virtue and shrewdness in wealth. Billionaires could even make a case of being equal to Arhats, more or less, as I currently understand this verse. 
This is made all the more odd on account of the Buddha's own rejection of wealth and kingdom.

Can someone shed more light? Are there two sets of guidelines that the Buddha advocated? One for those enmeshed in Samsara, and another for those gone forth?


  The Story of the Son of Mahadhana
  
  While residing at the Migadaya wood, the Buddha uttered Verses (155) and (156) of this book, with reference to the son of Mahadhana, a rich man from Baranasi.
  
  The son of Mahadhana did not study while he was young; when he came of age he married the daughter of a rich man, who, like him, also had no education. When the parents on both sides died, they inherited eighty crores from each side and so were very rich. But both of them were ignorant and knew only how to spend money and not how to keep it or to make it grow. They just ate and drank and had a good time, squandering their money. When they had spent all, they sold their fields and gardens and finally their house. Thus, they became very poor and helpless; and because they did not know how to earn a living they had to go begging. One day, the Buddha saw the rich man's son leaning against a wall of the monastery, taking the leftovers given him by the samaneras; seeing him, the Buddha smiled.
  
  The Venerable Ananda asked the Buddha why he smiled, and the Buddha replied, "Ananda, look at this son of a very rich man; he had lived a useless life, an aimless life of pleasure. If he had learnt to look after his riches in the first stage of his life he would have been a top-ranking rich man; or if he had become a bhikkhu, he could have been an arahat, and his wife could have been an anagami. If he had learnt to look after his riches in the second stage of his life he would have been a second rank rich man, or if he had become a bhikkhu he could have been an anagami, and his wife could have been a sakadagami. If he had learnt to look after his riches in the third stage of his life he would have been a third rank rich man, or if he had become a bhikkhu he could have been a sakadagami, and his wife could have been a sotapanna. However, because he had done nothing in all the three stages of his life he had lost all his worldly riches, he had also lost all opportunities of attaining any of the Maggas and Phalas."


I'd like to contrast this with another verse from the Dhammapada which is an emphatic put down of worldly gains. 


  Dhammapada Verse 178
  Anathapindikaputtakala Vatthu
  
  Pathabya ekarajjena
  saggassa gamanena va
  sabbalokadhipacce na
  sotapattiphalam varam.
  
  Verse 178: Far better than sovereignty over the earth, or far better than going to the abodes of the devas, or far better than ruling supreme over the entire universe, is (the attainment of) Sotapatti Fruition.
The PTS dictionary says,


  Dhana (nt.) [Ved. dhana; usually taken to dhā (see dadhāti) as "stake, prize at game, booty," cp. pradhāna &amp; Gr. qe/ma; but more likely in orig. meaning "grain, possession of corn, crops etc.," cp. Lith. dūna bread, Sk. dhānā pl. grains &amp; dhañña=dhana -- like, i. e. corn, grain] wealth, usually wealth of money, riches, treasures. 1. Lit. D i.73 (sa˚); M ii.180.; A iii.222; iv.4 sq.; Nd2 135 (+yasa, issariya etc.) Th 2, 464 (+issariya); J i.225 (paṭhavigataŋ karoti: hide in the ground), 262, 289; ii.112; iv.2; Sn 60, 185, 302; Pv ii.610; DhA i.238. Often in combn aḍḍha mahaddhana mahābhoga to indicate immense wealth (see aḍḍha) PvA 3, 214 etc. (see also below ˚dhañña). -- 2. fig. Used in the expression sattavidha -- ariya -- dhana "the 7 fold noble treasure" of the good qualities or virtues, viz. saddhā, cāga etc. (see enumd under cāga) D iii.163, 164, 251; VvA 113; ThA 240.


In summary it means something like "treasure": whether that's money or good qualities or virtues.

Some comments:


It can't mean (wouldn't make sense meaning) literally only 'money' because it says, " If he had learnt to look after his riches in the first stage of his life...,  if he had become a bhikkhu, he could have been an arahat" because though bhikkhus "accumulate virtue" they don't "look after money".
An origin story of the Buddha was that someone (I have forgotten who) prophesied that he would become a world-ruler or a spiritual emancipator (and his father wanted the former which is why he tried to keep him isolated in his palace, unaware of the wide world and of its spiritual needs).
According to what I've read e.g. (The Buddha's Teachings on Prosperity) Buddha doesn't condemn riches for the layperson. Although they're not ultimately or permanently satisfying (which is a reason why he suggests 'renunciation' instead, for monks), but riches are useful and there's some advice in the canon about how a lay person should fulfill their role within society.