@Sarah Albert, looks like you have an exciting opportunity, congrats!
Your risk tolerance is different from mine or anyone else on this forum so take advise with your own twist. The key issue is income vs expense and their associated risks. Even your income savings of $1000 may have some risk to it, but it may be tolerable (i.e. low probability you will lose it or it goes lower). If you feel good about the risks and your mitigation strategy , you should have enough confidence in moving forward.
Remember that even after your decision, you should reassess the risks so that you can mitigate them going forward. For example, you may want to have a roofing inspector give you an estimate (if not already) for a more accurate budget or periodically check on the furnaces/coolers to more accurately anticipate that expense. Having a plan to do things like this help optimize your opportunities and give you confidence in your decision.
One thing to consider is your cash-on-cash return. Cash of $4800 for $48,000 investment is 10% which is pretty good, but many like to see this a bit higher due to the unexpected expenses (risks), especially if you will spend $18,000 on a new HVAC system within 5 years. This would nearly wipe out your cash flow, so it's something you may want to get more information/confidence on for a buy/hold position and no plans to sell to cash in on the appreciation value.