A thousand ways to skin this cat so take everything I'm about to say, take with a grain of salt.
1. Although unsolicited, I would not even consider purchasing a house until I've paid off all my bad debt. i.e debt that isn't making you money. Credit card, student loans, etc. The reason I say this is if a bad day comes along, you don't want to worry about paying off your bad debt and a house payment. Moving on...
2. Have at least 3 months of savings in the bank, hopefully, more outside of any housing expenses to cover.
3. Now finally to your question. Well, a lot depends on the house you end up buying. Is the roof 15 years old, is the HVAC on its last leg, does the electrical panel need updating, has the plumbing been touched in the last 50 years? How old is the house? As a rule of thumb on my rentals, I consider 45% of the rent as "gone" before my mortgage. So using your $140,000 house I'll take a stab and say that would rent around $1,400 a month. That means you should expect to pay AT LEAST $630 a month in insurance, taxes, maintenance, and repairs. Well actually maybe a bit less since you don't have a property manager, so make that an even $500 per month. TImes that by 6 months and your talking about needing ~$3,000 if nothing goes wrong. As I write this, I'm not loving my answer but it should give you something to think about.