Final answer:
The terms 'suffers a house to fall into decay,' 'repair that which he might have kept up with a small charge,' and 'neglected by another' in the passage help define 'thriftless' as not being careful with resources, leading to waste and decay.
Step-by-step explanation:
The words from the text that most effectively indicate the meaning of the word thriftless as used in this passage are 'suffers a house that his father built to fall into decay,' 'repair that which he might have kept up with a small charge,' and 'neglected by another.' These phrases suggest that the heir does not use resources wisely or does not manage their property carefully, which highlights the meaning of 'thriftless' as lacking thrift or being wasteful and not maintaining what has been invested in. A thriftless heir, therefore, is one who does not take care of their financial or material resources effectively, leading to unnecessary expense and the ruin of property that could have been preserved with prudent management.