目前分词的用法问题

请视原句：

I can't even afford the streetcar fare going back home.

请问此句中的 going back home 于句内作何成分？其所修饰的是主语还是 fare？

I can't even afford the streetcar fare for going back home. for+动名词短语=介词短语，作fare的定语。

I can't even afford the streetcar fare going back home. 目前分词短语作时间状语，分词的逻辑主语为句子的主语。= I can't even afford the streetcar fare when I go back home.

下面为语料库例句：

Who's going to pay the fare for coming all the way out here, just to see a few rocks?