Learn Hardcore Spanish (Latin America): Mi hermano va a vender su bicicleta para que pueda comprar un ventilador nuevo. - My brother is going to sell his bicycle so that he can buy a new fan.

va a + infinitive is the most common way in spoken Spanish to talk about planned or near-future actions—just like English “is going to sell.” The simple future (venderá) also exists, but it’s more formal and can feel less immediate.

Why is para que pueda used here, and why is pueda in the subjunctive instead of the indicative?

para que introduces a purpose clause (“so that…”), and purpose clauses in Spanish require the subjunctive. You use pueda (present subjunctive of poder) because you’re expressing intention or potential—“so that he can buy”—not stating a fact.

Since the subject of both verbs is the same (my brother), could I say para comprar instead of para que pueda comprar?

Yes. When both clauses share the same subject, it’s more concise and idiomatic to use para + infinitive:
• Mi hermano va a vender su bicicleta para comprar un ventilador nuevo.
Using para que + subjunctive is only mandatory when the subjects differ or when you want extra emphasis on the purpose.

What does su bicicleta refer to? Could it mean “your bicycle” or “their bicycle”?

Here su refers back to mi hermano, so it means “his bicycle.” Spanish su can indeed be ambiguous (his, her, your, their). To avoid confusion you could say la bicicleta de mi hermano.

Why is nuevo placed after ventilador? Could I say nuevo ventilador?

Most descriptive adjectives in Spanish follow the noun: ventilador nuevo. Placing the adjective before the noun (nuevo ventilador) is grammatically correct but adds emphasis or a poetic/marketing flavor.

If the main clause were in the past—say Mi hermano vendió su bicicleta—how would the purpose clause change?

Sequence of tenses requires the imperfect subjunctive after a past main clause:
• Mi hermano vendió su bicicleta para que pudiera comprar un ventilador nuevo.