Is intention and purpose the same? Given that there are 'intentions' (cetanā) which lead (if they're not neutral) to either wholesome fruits or unwholesome fruits -- then is the same also true for 'purpose' (sankappa), i.e.:

Are there wholesome, unwholesome, and neutral purposes?
Which purpose could be 'wholesome' (if there is a purpose that fits that description)?
What is the difference between a 'wholesome' and 'unwholesome' purpose?
How could a wholesome purpose look like?

Definitions:

'Purpose': objective, agenda, goal, target (outwardly, 'more or less', 'near and far', 'time and place').
'Intention': state of ceto in action (inwardly)

Samples:

If your purpose is to accumulate (material things, a state of becoming): is it possible to maintain wholesome intentions?
For example: you like to have a monastery be built, you like to have a medi-community to grow, to be maintained.

If your intention is wholesome, is it possible to strive after a non beneficial purpose?

If your purpose is to let go (of material things, states of becoming): is it possible to maintain unwholesome intentions?
For example, you have buliding material and you are willing to let go of it, you have time and you are willing to let go of it.

If your intention is unwholesome, is it possible to strive after a beneficial purpose?
The wholesomeness and unwholesomeness and neutrality is decided by what you would perceive when you experience or feel the result. This is the differentiation between them. 

Generally aversion are painful when doing and so is when you get the result.

Generally clining based acts are pleasant when doing and also when you get the result.

Generally neutral sensations are when they are neither the above but still with the root of ignorance. 

The motivation associated with the purpose decides what is the result. This also has some sensation associated with it. This can be used decide what is wholesome or not when the volition is formed as detached observer as sometimes these minds spontaneously arise. (All 121 Citta has sensation associated hence any through arising is Dukkha - Dukkha Dukkha, Viparinama Dukkha, Sankhara Dukkha - whatever the sensation.) There are 7 roots which are Ahetuka (only enlighten person experiences this), Loba, Dosa, Moha, (unwholesome) Aloba, Adosa, Amoha (wholesome). When minds rooted in the above arise the Dukkha (painful experience, pleasant experience - unsatisfactoriness of change is pleasent experience, neutral experience - fabricated existance) or sensation associated with the roots are there also and you experience unsatisfactoriness in a subtle way. The sensation can be used to identify what the volition behind a purpose when the classification of the roots are not clear cut.

Though the action is same this might be might be motivated by different intentions or purposes in which case the results and wholesomeness will differ based on the motivation and what roots are present. Hence the Dukkha when volition forms and the Dukkha when the results do manifest will also differ accordingly, but distinction is from the Dukkha you experience or type of sensations. E.g. the purpose of a surgeon cutting a person is motivated to save the life but in the case of a robber it might be greed and aversion to kill and rob, but the action is same but the purpose is different. Also you maybe donating something to a allied country motivated block import of the same from another country hence indirectly economically sabotage another country, in which case you seemingly doing good but the purpose is not. With the volition you experience the sensation associated the root and many more times amplified when you experience the fruit.

Intention, action and result decides the karmic formation. Sometimes good intention may not result in positive outcome nevertheless the though does bear fruit perhaps not as weighty as a rebirth linking Karma. If you have the intention but not follow though you still have a weak Karma. If you have intention and follow through and the desired result happens then this is a more intense Karma. Whatever the case motivation decide the feeling associated resulting experience and also see it when the volition forms. The taste of the fruit you take and plant will have the same taste and the fruits the tree would bear. Intention is the initial fruit from which you take the seed to plant.