Theory:

     She was silent for a while, taking in this information. Then she said, ‘And you’d like to buy it back now, but you don’t have the money?’ He did not look very prosperous.

     ‘No, I wasn’t thinking of buying it back, wanted to see it again, that’s all. How long have you lived in it?’

     ‘Only three years,’ she smiled.

     ‘Would you like to come in and look more closely?’

     ‘Wouldn’t your parents mind?’

     ‘They’ve gone to the club.’ They won’t mind. I’m allowed to bring my friends home.’

     ‘Even elderly friends like me?’

     ‘How old are you?’
Explanation:
 
She was trying to sink in what the man told her. She thought that maybe he wants to buy the house, but he didn't have enough money. The man didn't look wealthy now.

The man told her that he was not thinking of buying back the house and that he just wanted to see the house again. He asked her how long they had lived here.

She said that she lived there for only three years and gave a smile to the man.

She asked if he would like to come in and have a closer look at the house.

The man asked if her parents would allow.

She told him that they had gone to the club and that she was allowed to bring her friends home.

He was still not convinced and said if even elderly friends like him are allowed inside the house.
 
She immediately asked how old he was?
 
Meanings of difficult words:
 
Number
Word
Meanings
1.
 Prosperous Wealthy.
Reference:
State Council of Educational Research and Training (2018). Term-1 English Standard-9. I Can’t Climb Trees Anymore - Ruskin Bond (Slightly adapted) (pp. 157-160). Published by the Tamil Nadu Textbook and Educational Services Corporation.