Exegesis:
tis gar ex humōn ‘for who of you…?’ gar connects what follows with the preceding statements. This connexion is that the very requirements for discipleship make a conscious decision necessary. tis introduces a rhetoric question, the obvious answer being: no one.
thelōn purgon oikodomēsai ‘planning to build a tower.’ thelō implies here purpose. purgos may refer to a tower of a vineyard (cf. Grundmann).
ouchi prōton kathisas psēphizei tēn dapanēn ‘does not first sit down and calculate the cost.’ For ouchi cf. on 4.22; for prōton cf. on 6.42. kathisas goes with psēphizei and suggests serious and prolonged consideration.
psēphizō ‘to count,’ ‘to calculate.’
dapanē ‘cost,’ ‘expenses.’
ei echei eis apartismon ‘(to see) if he has (enough) for completion (of the building).’
apartismos ‘completion.’ eis apartismon is virtually equivalent to final apartizein ‘to complete.’
Translation:
For shifts to a suppositional or conditional clause, or to second person forms, cf. on 11.5.
Tower. The reference is to something relatively big; other semantic components of the term e.g. that a tower is high, or serves as a look-out, are not specially relevant in this context. Therefore a generic rendering, such as ‘big building,’ may be preferable in cases where the rendering used in 13.4 does not fit.
Count the cost (i.e. the building cost), or, ‘calculate what it will cost,’ ‘considers what he must pay’ (Sranan Tongo).
To connect the clause whether he … complete it with what precedes one may have to insert, ‘asking himself,’ ‘in order to know’ (Kituba), ‘to see’ (Thai 1967, similarly Lomwe, one West Nyanja version). Whether may have to be rendered by a positive-negative expression, ‘whether or not’ (Shona, similarly Pohnpeian). In some cases a shift to a direct question will be preferable.
He has enough to complete it, or, ‘he has what is needed to finish it,’ ‘he has that which will finish building it’ (Zarma), ‘he is with all the money that-will-be-required’ (one West Nyanja version).
Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.